I don't like the idea very much. We know each others' reputations through experience, and newbies do pick things up fairly quickly, especially here. The thread rating system doesn't seem to get used.
If it was brought in, I'd suggest a thumbs-up/thumbs-down system. Each post has a thumbs-up and a thumbs-down icon which each member can click once, affecting the posters reputation. Of course, if someone becomes particularly angry at someone, they will just search for all of their previous posts and go on a thumbs-down spree, but any system will have that problem.
