(a) willing to keep themselves to a high-enough standard to think for themselves and see that it's a grey area (that they might have a bias for one side or another). You can't just assume the top post is definitely the right thing, even with a good number of upvotes.
(b) willing to read more posts further down, giving them plenty of respect, and contribute to the conversation.
Maybe a better way to rank comments is something more probabilistic rather than just ranking by (num_upvotes - num_downvotes). (Actually, how is it done now?)