I posted a couple times on an LDS forum awhile back (lds.net). They had a very simple rating system: there was a button, by the "reply" button you could use to give someone a "thank you for this useful post" or a "laugh out loud."
Laughs were meant to be used for humorous posts, but they often got used to laugh
at people who made points that were thought of as absurd. So, I wouldn't suggest that. Maybe there could be a "smiley face" option: then people wouldn't have to waste a post to smile. Of course, CS's post rate would go way down if that were the case.
I think the "thank you for this useful post" worked fairly well: every message had a little section beneath it that listed all the people who said "thank you."
The only semblance of a reputation, rating or score was a running tally of the laughs and thanks a person got.
Since the crowd here is a bit more intellectually oriented and (generally) objective, I think a more sophisticated system is appropriate and workable here. But, something simple like the lds.net system could be a way to break in the concept.
-Bluejay (a.k.a. Mantis, Thylacosmilus)
Darwin loves you.