Nice experiment. There's an issue with curly braces { }. When typing in Russian (and in other Cyrillic languages) you need to switch keyboard layout before and after each curly brace. It quickly becomes tiresome to do: type-in-russian, switch-layout, type-{, switch-layout, type-in-russian etc. This problem also exist in Markdown too: square brackets [ ] and curly braces { } both live on the same keys as Russian 'Х' a…
Out of curiosity, do Russian developers permanently use an English layout, or just map these keys elsewhere?
Hence, many many developers use a US layout instead of their native one, even if their native one is somewhat similar to the US one. This is true for pretty much all European layouts and certainly for more foreign ones.
Its a mess, basically.