I like your thinking. @danmaruschak had a good idea that rewards could go via an exchange and then they'll be completely anonymised - the downside is it would have to be done manually. So I'd probably work on a "monthly league table" approach of some sort which is stored in the background. Users can see their own league position (as an incentive to increase their ranking) but nobody else's.

With PAPs that are simply crappy accusations, once a level of "this is crap" is reached, then that PAP could have a lower priority to appear within the game so fewer people see it. And similarly, if somebody repeatedly posts crap (or the continually choose the "wrong" result), their reputation will be lower which will make it harder for them to climb the league. I think that building in these kind of controls should be straightforward too.