With Slashdot, anybody can vote. Often, trollish behaviour gets rewarded with points, because, well, because trolls can vote too! Before being able to vote in the system I proposed, you have to have demonstrated to the current moderators (voters), that you are someone that on average posts interesting, thought-provoking stuff.
I don't know whether this would actually work, but it seems at least reasonable, and as far as I'm aware, it has not yet been tried