the thing is it must have already big database of movies and enough users, only other sites meeting this are rotten tomatoes (disabled read only forums so apparently not interested), TMDb (nothing, seem they are not interested in this opportunity judging by discussion in their forum), Metacritic (nothing), Letterboxd (nothing and too few users) and trakt.tv (has threaded comments for specific movies, but also not that many users)

i talked with my friend running one of the biggest subtitles website who had obviously enough database of movies and TV shows, but he ain't interested because of legal responsibility for content of comments and need of expensive moderation, though i would think this could be outsourced to Disqus and legally comments would be stored on their servers