Well I gravitate towards the opinion that OP is at least exaggerating his accusations.
But if Ratimov is indeed a serial plagiarizer I'm sure a Russian speaker would be more able to tell if this is true or not since he is so active on the Russian subforum.
We are not tolerate to plagiarism in Russian board, you can see that there are several active plagiarism fighters from Russian board on the forum and we report plagiarism in Russian sections as well. So if there is any plagiarist in Russian sections it wouldn't be unnoticed. We have a big enough local board and like it to stay clean and comfortable for communication.