Today I deactivated all Beta features. First: the talk-pages are only in English. I don't know whether I could only post feedback in English or in other languages and I know, many people don't give feedback at all because of this. Second: I will not test any software from the WMF, until the Foundation keeps the superprotect right, which is a thread to all communities.
Topic on Talk:Compact Personal Bar
Yes, you can give feedback to any feature in your preferred language.
About ability to filter our messages in your language: discussed here.
(No comment on the second part; left a commentary at this page instead.)