im pretty sure alot of people know when they post offtopic. in most cases its not because they want to destroy the discussion. its because you want to share something.
Its kinda annoying to read so many offtopic stuff when just want to follow a specific topic.
(happens rarely to me but it happens)
also alot of posts are adressed to a small number persons who pretty enjoy them, all others just see crap in it. i can only speak for myself, i really would appreciate this option. (for example: i dont want to force everyone to read my shit when i am trolling komo.)