you can give people's posts postive or negative feedback by clicking the little
icon inside each post. i think this is how the board figures out your reputation. (and, of course, the admins could probably cheat and give themselves, or anyone really i guess, a bit of a head-start in the reputation department)
i gave jep negative feedback once.. but i'm too lazy to use it regularely.
oh, and i think that little green block in each post (under the "Posts: ###" line) shows roughly your reputation.. maybe as you gain positive reputation stuff you get more green blocks?