I'm sure there's a good reason, and that this is a dumb question, but why would it not make more sense just to have one bilingual website?
I'm an old man and a "newbie" on SE, and since I don't have enough points yet to comment on someone else's answer I'll answer the question myself: As for me, being a philologist, I think SE having a completely Russian forum for the Russian language was/is a very, very, very, good idea.
In fact, such a very good idea that in my very recent answer (in Russian) to a question (in Russian) I suggested to the questioner that he might want to ask the same question in the SE Russian language "Русский язык" Q&A forum. I said/say that because that forum obviously appears to have many more Russian-speaking users who might also want to answer the question than is possible in this mostly English-language "Russian Language" forum. For now, until my knowledge of the Russian language increases, for my Russian translations I use the computer technology of Artificial Intelligence available to me (and everyone else) of Yandex.ru's translator -- a language classroom available to any and all who have a mind to use it as such.
I haven't had the time to do it yet (I'm a new member currently registered in nine SE forums that are of interest to me), but I'm guessing that when I do get around to reviewing the questions and answers on "Русский язык" I'll find it supports my conjecture -- knowing how Russian is written correctly by Russian-speaking people is far better than substituting correct English word order and grammar in Russian-English translations.
Russian grammar and word order is so distinctly different from English word order and grammar that translating good Russian into good English really grates on my nerves! I want to be able read and write Russian in the same way that Russians do, and the extensive examples of correct Russian word order and word usage is very important to me -- and should also be so to English-speaking students who really want to learn to read, write, speak, and think, in the Russian language in the same way as Russian-speaking peoples in the Russian Federation and surrounding countries do.
And SE's "Русский Язык" forum helps me -- and others like me -- to do just that.