I agree that the Russian comments shouldn't appear in the English version, but I could miss an English comment because it was mistakenly posted as Russian.
I think we don't need to choose if the comment is in English or Russian, as it can be detected automatically if it's English or Russian. A simple way to do this is to check if the comment contains any Russian letter which does not exist in English (I don't understand Russian, but I think there are many such letters).
Edit: Now I see that if you are writing a comment in the Russian version you can't choose English for the language, it's Russian by default and you can't change it.