It can.

Anything that makes the reader stop and think is likely to slightly derail the readers train of thought. It's a risk their attention doesn't return to where it was before.

This is always the case. Indeed it is sort of necessary for storytelling; you need new thoughts to be conjured and old ones forgotten. The trick is for these to be consistent with where you want to take the reader. If the difference in culture of the character or the story is something you want to place emphasis on, great. If it's incongruent there is every risk it interrupts a train of thought you wanted and replaces it with one you don't.

I think of it as having very similar logic to that of Chekhov's gun.

Things to note:

• It's likely not to be a big distraction and, like others have pointed out, if the reader really is immersed and wants to return: this is unlikely to prevent them.

• It will come up a lot if it's a major character but after a few views, each will be even less distracting.

• This is more of a question about the reader than the text. Pretty much anything could either jar or resonate with someone. There's no way to be certain, even if it's a cliche like calling your cow "Daisy", that won't set someone down a different path, like: "that's a bit cliched", and break immersion. The only thing you can do is be mindful of what's likely impact is for your audience.

EDIT below:

Upon reading my answer, I thought there might be a way to make my thoughts clearer: exaggerate them.

• You can use a name that's impossible to pronounce: Say you want an, alien - everything is new and confusing - science fiction/fantasy, world. Want to show the protagonist out of their depth within it? Have them meet a character they have trouble referring to because their name is a particular shade of purple. This shouldn't damage the immersion. To the contrary: if that makes sense let alone would work, might be exactly the sort of thing you might want for your readers to pondering for the sake of immersion. Casually introducing this creature as "Peter" will ask questions that, if you don't have the answer to, will probably harm that feeling.

• Or just need a rudimentary understanding of the classics to have a stab at: Say you want to play off the idea of an eccentric artistic type, it's not wrong to have them had their name changed to the ancient Egyptian hieroglyph for "axe-in-a-block-of-wood".

However: if there is no reason to do this, and the reader is not expecting it and you deviate from the Latin alphabet: it's going to linger with them until you explain why.

I also thought it may be worth noting, as has been mentioned, that there is a slightly separate issue that may come up in tandem: Names that are difficult to parse.

Say I tried to write this using html colour codes to get a shade of purple or used some academic representation of the hieroglyph. Even with the context of the question, that might trip someone up. Not something to lose sleep over, but it wouldn't add anything to the narrative. The finer points of representing hieroglyphs and why I have syntax highlighting aren't relevant to the narrative. Don't force your readers to tackle them and they will stay focused on what you want to tell them. If it's necessary to avoid calling your alien "Bob" though...

First of all to answer your question directly: Yes, to some readers – like your friend – it will break immersion. This doesn't mean it will break immersion for everyone, nor does it mean that it's necessarily a bad choice to use these types of names, but for some people it will just cause frustration that takes them out of the story.

Assumptions:

• Everyone will to various extents appreciate names that fit the world you build
• Some will get distracted each time they encounter a name they can't pronounce

Approach A: Nicknames

Introduce a character who has trouble pronouncing the name and gives the character a simpler nickname.

"I am duchess Mrstttkya Sjshya, it's a pleasure to meat you" "Thank you, duchess Sj... Sje..." The Duchess sighed and interrupted "I understand it's hard to pronounce for your people, 'Duchess Sasha' will do just fine"

This works particularly well when you have a foreign main character or the main character encounters foreign characters.

Approach B: Hand holding

Accept that it will be distracting for some readers, but try to make it as easy as possible for them by extremely clearly explaining how it should be pronounced. In Harry Potter and the Goblet of Fire you find a somewhat similar setup to Approach A, but instead of going with a nickname the character in question explains how the name should be pronounced:

Hermione was now teaching Krum to say her name properly; he kept calling her ‘Hermy-own’. ‘Her – my – oh – nee,’ she said, slowly and clearly. ‘Herm – own – ninny.’ ‘Close enough,’ she said, catching Harry’s eye and grinning.

In high fantasy especially this is sometimes skipped entirely and footnotes or other complementary text is used to explain the correct pronunciation.

Approach C: Minimize name use

Give each character a proper complex name, but whenever possible use different terms to refer to the characters. One book I read was written in first person where the main character was alone in a survival situation for two thirds of the book and his name (which was ridiculously long even for fantasy/sci-fi standards) only came up three or four times.

Approach D: Hide behind the translation

Typically when in a situation where foreign names come up we are talking about stories taking place in foreign cultures entirely (cases where approach A isn't an option). In those cases there is typically the assumption that those characters are not speaking English, yet the story you are reading is written in English.

The same can apply to names. Some authors will make this explicit such as Tolkien:

To their man-children they usually gave names that had no meaning at all in their daily language; and some of their women's names were similar. Of this kind are Bilbo, Bungo, Polo, Lotho, Tanta, Nina, and so on. There are many inevitable but accidental resemblances to names we now have or know: for instance Otho, Odo, Drogo, Dora, Cora, and the like. These names I have retained, though I have usually anglicized them by altering their endings, since in Hobbit-names a was a masculine ending, and o and e were feminine.

Whilst others will leave it implicitly. Anyway, the point is, according to Tolkien's mythos Bilbo Baggins was actually called Bilba Baggins, but that doesn't mean that it's necessarily the right decision to write that in your book. In the case of Bilba the problem was that it sounds feminine rather than pronunciation issues, but the approach can still stand.

Conclusion

What approach works the best of you depends a lot on your setting and genre. In high fantasy the expectations of the reader and the investments the reader is willing to make are very different from a young adult fiction novel. Still the most important advice I can give is to have people read your novel before publishing it and listening to their feedback.

Foreign names don't break immersion..... in fact they enhance immersion.

If the CEO of a fictional mega Korea corporation were named Dan Smith that would break immersion.

However, a hard to pronounce foreign name does deter a lot of less sophisticated readers.

One of my friends calls ALL Asian leaders Ho Chi Minh.... He isn't a racist. He just can't process non-english names. So he just substitutes the only name known to him to every asian person.

So imagine him reading a novel with foreign names...

I generally like to write that names are "anglicized" if they are indeed made up for the convience of the reader. For example, I once wrote an alien main character named "Kyron" and even then, I have at various times changed pronunciation in my head and had it pronounced it "1st syllable rhymes with sky (Kai-ron)", "1st syllable sounds like key (key-ron)", "1st syllable rhymes with beer, second sounds exactly like on (Keir-on) or second syllable sounds like ron (Keir-ron).

I don't know and have thought maybe all four were valid and different characters said different versions of the name based on their own accents and how they heard it... since there are about 5 other characters, each one could have a personal preference and the fifth is like "Wait... who's pronouncing it right?" and the original conversation is sidetracked in debate over the matter.

Speaking as someone who has a real name that is essentially a varient pronunciation of another more common name people will constantly mispronounce my name by mistake, (Shane (sounds like... well if you find a rhyme I haven't heard, I'll give you a cookie... but Train is a good word that rhymes), which is the pronunciation of the name Sean in an Ulster Irish accent, where as in America, Sean is often pronounced Shawn (sounds like Brawn)). "It's Shane" is practically my catchphrase, due to how often it happens. In fact, I had a teacher in my elementary-middle school who legitatmently taught me in almost every grade and is a family friend and to this day occasionally calls me "Shawn" by mistake... though the real winner of "You should know better" award was the mother of one of my best friends. His name is Sean and I'm Shane and his poor mother would often swap our names when talking about both of us.

Suffice to say, if your character has any contact with anyone with less familiarity of her name, she will be well aware of the mispronunciation. Like me, it wouldn't be much to suggest that she's developed a quick habit of pronunciation correction every time she hears the mispronunciation... I would say write the line once a book so your readers get it but it doesn't become forced... and maybe at funny bits (like in the middle of a fight at the heart of a volcano that's about to erupt, have a bad guy the wrong pronunciation only for her to casually correct it, while tossing 4-5 ninja mooks to their magma deaths below... Sure the fight is difficult, but correcting someone's pronunciation of my name is pretty on par with thinking about breathing.

I don't think strange names break immersion; I think names that cannot be sounded out (correctly or not) break immersion.

"Hermione" can be sounded out. "J'xyx'brtl" is too hard to sound out, and for me would be likely to break immersion every time I see it, because my reading system stumbles over it.

But whether readers get "HER-My-Own" or "HER-Me-Un" or "Her-MY-Oh-Nee" doesn't make a difference, their eyes can glide over "Hermione" without a stumble.

For "Jiolluav" I would probably read "JOLE-Uf", similar to "JO-seph". I wouldn't have a "Zh" sound. In my fiction, names are one, two or three syllables if common (like "Christina"), mostly two syllables. If they need to be longer, I may give them a nickname as well, for dialogue.

Making reading difficult; by using hard to read names or foreign or alien words, by twisting grammar, are ways the text itself can break immersion. Making a reader read a passage more than once just to understand it is (IMO) bad writing.

While it's going to vary between readers whether it bothers them or not I have to say I'm firmly in the camp that it can ruin immersion.

I'm not too worried about whether I "pronounce" a name "correctly" or not - but if the way the name is written doesn't parse easily then I find it incredibly hard going to read.

That said with your example name "Jiolluav" I would probably not have had a problem when reading it - I would likely have just gone straight to the "Jollav" pronunciation your friend used.

You could always make a note in prose of how it is said. For example, in Matthew Reilly's Scarecrow (and one other book for which this is arguably a spoiler), there is a character named Aloysius. At the very first appearance of this name, the prose notes that

he pronounced it allo-wishus

which immediately clues in the reader to how it is said. If not for that, a reader unfamiliar with the name might think of it as "a-loy-see-us" or such.

Whenever you have something a bit weird and difficult to easily explain – where you have to educate the reader – do it through the presence of an Everyman Character who the audience better relates to and who themselves struggles with the concept.

In this case, have the character struggle with the name. "Jiolluav" as a string of letters is hard to remember, and doesn't follow normal rules for names in English (or existing foreign languages for that matter). Furthermore, the pronunciation "Zholl-you-of" is non-standard and doesn't follow from how people generally understand words to be pronounced. Therefore, the 'everyman' character needs to struggle with the name, and actively create some form of mnemonic to remember it and avoid insulting this Jiolluav person. This can be mentioned a couple of times more (and maybe even made fun of), before the everyman (and concurrently, much of the audience) get used to it.

This way, you can turn a frustrating and obtuse bit of worldbuilding into a memorable feature of the work.

Hard-to-pronounce names suggest a different culture. If War and Peace had its characters named not Andrei Nikolayevich Bolkonsky and Pierre Kirillovich Bezukhov, but Andrew Bolk and Peter Bek; or if the characters of the Kalevala were named not Väinämöinen and Joukahainen, but Van and John, that would ruin my immersion. It would break my immersion because the names would not match the culture presented.

As a reader, if I encounter a name I don't know how to pronounce (e.g. certain Welsh names in the Mabinogion), I pronounce it the best I can, and move on. If I am informed of the "correct" way to pronounce the name, I amend what I thought the name should have been pronounced like, and stick to the correct pronunciation. I see no problem there. (And I've never heard of anyone claiming they can't read the Mabinogion because they don't know how to pronounce the names.)

If you care about the readers pronouncing the names correctly in their heads, you can provide a pronunciation guide. Tolkien did this with The Lord of the Rings, others did it too. A pronunciation guide doesn't assure, however, that readers would actually follow the pronunciation you have in mind. For one thing, it can be somewhat hard to explain in writing what sound you have in mind. For another, if you put the pronunciation guide in the beginning, it's not sufficiently interesting, the readers are not yet sufficiently immersed in the story to care, they might well just skip it. And if you put the pronunciation guide in the end, it's already too late - the readers already have the "wrong" name in their heads, and they've already finished the book anyway.

An alternative is to add some hint within the story. A name can be woven into a bit of verse, so the rhyme helps the reader understand how the name should be pronounced. That, however, requires work, it might not be natural to your story, and even if it is, you wouldn't do that for every single character.

In short, no, hard-to-pronounce names do not break immersion.

However, if the names you plan are particularly long, you might find this discussion of long names helpful.

I don't care about pronunciation, because I rarely pronounce even semi-common names correctly. I have trouble with even some of my own characters' names. But then, for me, written language and spoken language are far more separate in my head than they are for most people (which is why I always spectacularly failed spelling tests in school).

I do care about remembering the name. If I confuse two characters because their written names are similar (even if they're pronounced completely differently), that's a problem for me. Even worse if I don't realize they're separate characters.

I would pronounce your example name GEE-oh-love. Completely wrong. But, as a reader, I don't care. I only need something in my head so I can remember her/him.

Yes, I find it distracting. To me, the problem is not so much if a name is hard to pronounce, but if it's difficult to figure out how it's supposed to be pronounced.

Unless the spelling of a name is somehow important to your story, if you're going to use made up names, I'd say to spell them phonetically. If Jiolluav is supposed to be pronounced Zholl-you-of, then why not just write it "Zholl-you-of"?

This is especially true if you have multiple difficult to pronounce names that resemble each other. If there's a character named Jiolluav and another named Jaolvual, I think readers may well get them confused and find themselves constantly checking back.

Sure, in a fantasy or science fiction novel, I expect names to be unusual-sounding. If you're alien from the planet Rigel 7 is named "Roger Smith", that would be very distracting. But don't give me a name with a baffling pronunciation, like Wadlkjaece. Give me something phonetic, like Wa-juto-case or some such.

You can criticise me, but if I get a name like the one you have used (I can't easily see how you get to the pronunciation you give), I simplify or skip it. The consequence is that hard-to-say names get forgotten. Trying to work out who is who does break immersion. An alternative, assuming you don't want to change the names, is to spell them more phonetically.

I’m only going to give my view as a foreign English reader.

It doesn’t matter, I’ve found out I mispronounced Elminster, Hermione and half of the names on the Lord of the rings mythology. It didn’t break immersion cause I would just pronounce the names (in my mind) as it would fit me and hence it will always sound natural (to me).

An unknown reader will not know better so he’ll make up the pronunciation as he sees fit and carry on with it. The word itself will evoke the made up image of the character in the reader’s mind and they will become linked disregarding how you intended the name to be pronounced.

Your friend has troubles because you tried to force him into a given pronunciation when he had already decided on something else. That’s what breaks immersion.

Pronunciation guide, for me at least, is counterproductive, reader is interested on the story, not in a linguistic class.

Like your reader, if I'm unable to pronounce a name, I replace it with something simpler so I don't have to try to pronounce it each time I see it. After the first few times of seeing it and trying to get it right, I'll just replace it (once I really get into a story, I barely even see the correct spelling). For instance, I pronounced "Hermione" as "Her-Me-own-ee" for the first handful of Harry Potter books (until I saw the films). That's not quite the same as your scenario, but it's along the same lines.

Because a reader is apt to use their own pronunciation, I don't think it necessarily breaks immersion. You can't expect all your readers to adhere to your desired pronunciations. It's just one of those things, if you choose to keep it, that's in the readers' hands after you send it out into the world.