Another solution: make down votes "cost."<p>If a user hits the down-vote then a comment box opens <i>requiring a reason</i>.  I don't mind down votes, but I can't stand not knowing why.  It's like a (bad) dog owner who comes home and beats the dog for pooping on the rug.  Poor dog did that hours ago and thinks hes getting beat just because owner came home.  No lesson learned and it fosters a poor relationship between the two and encourages "acting out."<p>Additionally, if "the reason" received n down-votes HN could automatically cancel the DV to the original comment.