I think I'm scrapping that idea; I took it to its logical conclusion and it was quite messy (think something similar to Parallel World mafia, except not parallel. The users would attempt to find and ban the trolls in one thread, while the other thread would continue as a normal game of mafia -- with the same people, of course... *end rambling*)
Of course, that's completely different from what I originally intended; what I originally suggested was more akin to a normal mafia game with unique roles.
Here are some of the roles I had considered before giving up:
Newb (T, M) - Every day, one of your posts must contain one of the following: OMGUS, rolefishing, bandwagoning (with no reason). The content of aforementioned post must be less than 30 words.
Vengeful Newb (T) - You must OMGUS the first person to vote you each day. You may not remove your vote from them until they apologize for suspecting you.
Grammar Nazi (T, M) - If you find a grammar or spelling error in someone's post, you may write a post attacking them for it. Their action will be redirected to you for the night.
Explosive (T, unaligned) - If you ever get more than three votes on you, ALL YOUR POSTS MUST BE IN CAPS AND CONTAIN EGREGIOUS INSULTS DIRECTED TOWARD THE PEOPLE VOTING FOR YOU. YOU REQUIRE EXTRA VOTES TO BE LYNCHED.
Vengeful Veteran (T, M, unaligned) - You hate it when people vote you. Why won't they just listen to you!? The first person to vote you becomes your lynchee. You must lynch them as well as fulfill your primary victory condition to win.
etc, etc.
Most of them would only work in a closed-role setup anyway.
But onto better things:
Has anyone tried a post restriction mafia before, loaded with roles that have various post restrictions on them but is otherwise completely normal?