There won't be any downvote/dislike button and... I don't support this.
Yeah I wasn't talking about anything that would seriously down-grade a users rating or anything, just see a lot of these posters in the marketplace.
I have suggested a function 'identical' at you, but only when an user is banned. He will lost X points every ban, in this way I am sure he will learn the forum rules and stop to 'spam' (because if he will continue, he will lose his rank - downgrade).