If you happen to use cyrillic in your source code (for comments or even strings) and constantly switch between latin and cyrillic, then this actually happens with а "c" letter, because both latin and cyrillic "c" occupy the same button. And that's not fun, btw.
Depends on which keyboard layout you use, of course.
Russian is my first language, but English is my primary language, and I never had my chance to practice typing using the standard Russian keyboard layout, so I almost always use the "Phonetic" layout - where the latin c is the cyrillic ц. (Also, w is ш, and who the hell remembers what []\-= map to - always trial and error for me to find южэьъ.)
