I support not feeding the clueless, but I would like to emphasize that that policy should not bleed into a lack of explaining downvotes of otherwise clueful people. There aren't many things more aggravating than participating in a discussion where most of my comments get upvoted, but one gets downvoted and I never find out what the problem was--or seeing some comment I upvoted be at -2, and not knowing what I'm missing. So I'd like to ask everyone: if you downvote one comment for being wrong, but think the poster isn't hopeless, please explain your downvote. It's the only way to make the person stop being wrong.