I have used other forums and social networking areas where there is a 'thumbs up' and 'thumbs down' icon that other posters (not the one who posted) can click on for helpful posts (or unhelpful).
How about introducing that here, and also all 'up' clicks get a point (but no negative points for down thumbs, too easy to get silly). Then when a person has say 100 points the player can 'cash in' the points for experience points at say 10 exp to 1 help point?
This would encourage and reward helpful posters, the lack of any use to down thumbing would limit and negative side to this, and so long as it's only exp being traded there would be no issue with credits and cash. The only thing is you would have to watch for multis, but then this may even aid their detection. That is of course if WGT want to detect them.