No, it's not an issue with all UTF-8 character input—it's a crash that happens in specific situations. In other words, it's intermittent. For example, there were cases where accidentally typing Korean characters while opening a terminal or editor would cause a crash. (This was about 4 years ago, so I'm not sure how it is now.)

Anyway, it's been mostly fixed now, but if I remember correctly, there were cases where edge cases caused crashes because the input standards were inconsistent