You might know of well-known Soviet musician Viktor Tsoi, whose name in Hangul is 최 and in Cyrillic is Цой.
The thing is that now his name seems to be written as 초이. My guess is that it has something to do with 최 being pronounced as [t͡ɕʰwe̞] ~ [t͡ɕʰø̞] (according to the Wiktionary entry for that syllable). What changed? Is 최 ever pronounced as [t͡soj], for example in Kimch'aek where his ancestry may be traced back to?
Not that related to this question, but it WAS pronounced as [oj](somewhat like boy[ɔɪ], but different, though) in medieval Korean.
Not now, of course.
additionally, [t͡s] is ㅈ in north Korean pronounce.(and ㅊ is [t͡sʰ] in north Korea.)
The Korean Wikipedia, like other Wikipedias, has strict rules on how to name articles, and editors who are ready to fight for these rules.
My best guess is that since Viktor Tsoi was Russian, the editors applied the standard rule for transliteration of Russian names. It kind of makes sense: he grew up in Russia, so I assume how he pronounced his name would be different from a native Korean pronunciation of 최.
On the other hand, I think Koreans (outside of Wikipedia) usually use 빅토르 최 when referring to the singer: Google gives 108,000 hits for "빅토르 최", and 14,400 hits for "빅토르 초이".
