If not only bug questions are viewed, why we are asked to write only bugs in both languages - Russian and English. Does it apply to feature requests too? Or how developers differentiate which proposals require development and which don't?
The workflow itself discussed in the What is Stack Exchange's workflow for handling bugs and feature requests? (thanks @Shadow Wizard).
Question about languages of a post: General idea here is that we want developers understand all information addressed them without somebody's help. It means if you want a feature-request gets implemented probably it's better to write it in English at least. At the same time not all users of an international site want/like/can discuss feature requests in English, so it's worth using the language of a community too (otherwise, probably, it's better to post a feature request directly on MSE).