Perhaps the genre could map to a tag (if tag with genre(s) exists on forum, automatically apply tag when discussion is posted).
This could also apply to your IMDb extension, but in both cases would probably be dependent on hrvoje_hr suggestion as you'd probably want to query the backend APIs and retrieve genres prior to creating the discussion so it could be tagged in the process.
That functionality might be integrated better with Clarks taxonomy extension (if made v1 compatible), which if I understand it's capabilities could allow for tagging anything you want including genres, release years/decades, rating, actor/actresses.
