I think the problem with Russian names in particular is that a Russian name has three parts (e.g. Nikolai Ivanovich Lobachevsky) and different parts get used in different contexts, depending on who's speaking, level of familiarity and so on. So it's like in an English novel where someone might be referred to as Smith by the narrator but John in dialogue, but with an extra 50%, at least, of confusion.

The obscure Russian nicknames! How is anybody supposed to know without being told that Sasha and Alexander are the same guy? (I do realize that while some English nicknames like Johnny for John are pretty self-explanatory, other like Jack for John or Dick for Richard are as opaque to foreigners as Alexander/Sasha)

I haven't read any Dostoyevsky since high school, and don't remember it at all, but I'd imagine it has to do with nicknames.

A non-Russian speaker is going to be confused when the same character is referred to as both Alexander and Sasha, for example, and will think they're different people.

Mostly Southern Chinese or Hong Kong.