I don't know..this might be a shitty idea, but what if we had a number next to our usernames that told us what percent of our posts were well received. It could be something like a mix between Facebook and Reddit; there will be an up and down thumbs or arrow or something and you can vote on any post that is made in the forums.
If your average goes below lets say 20% then you are banned for a week.
this would help prevent spammers and be a really good system to also show off the best posters.
TO PREVENT just voting down every post, only people with averages of OVER 70% could vote. (we will choose a few to start)
As for "Gpr" thats the first acronym i could think of. Good Post Ratio.
Any other ideas/thoughts?