I think there is one for instruments, haven't seen it surface lately (I'm behind in practicing the ones I play now, new ones aren't on my radar!)...
As to languages, I tried a conversational French thread on the old Forum, but it got sort of clunky with the requirement to translate everything into English as well....so it did go for a little while, but died.
Neither were exactly like the "encouragement" threads for runners, readers, etc., so a different approach might indeed work.
Good idea, at any rate.
M.