This is one of those things I feel hasn't scaled very well, but there's no really good way to deal with it. Its worth remembering we'd have similar issues with flags on pt, ja and ru (or potentially language sites).
Autotranslate... dosen't necessarily work that well, it adds an additional layer of complexity to the chat system (the translate easter egg for mods for example. kinda breaks a lot and you add an external API as a dependency). We also assume there's some sort of standard way of writing - while these cases are in properish russian script, transliteration's pretty common, especially in indic languages, and there's often no standardisation or support in translation APIs. You'd need to identify, transliterate, make a best guess and then translate.
We might also miss some cultural nuance in seeing whether something that seems inoffensive is offensive.
Kinda tempted to go "Maybe give the Russians, pt.so and ja.so, and other similar language sites their own chat server" but that probably adds to complexity - you have a few sites with no oversight. And one or more chat server with its own set of mods for no real reason. Letting rooms handle their own things also works some times but not others depending on the people there. A independent chat server just for non english sites (or separating out moderation for such chats)... could end up messy (or work out gloriously - but if it would go well, we wouldn't need to stick em in their own server).
There's no really good answer IMO - I tend to ignore these (figuring someone who reads Russian will handle it), I've occasionally heard suggestions that "if it isn't in English, just mark it valid" or ping the appropriate mod (which doesn't scale).