As a frequently downvoted commenter on HN, I've done a lot of thinking about this mechanism, and I would like to propose a change to it.
Since the goal of HN is to encourage discussion and debate, why not require a reply to a comment before you can downvote it?
This would change the negative, conversation stifling enablement into one that requires a person to contribute to the discourse before voting their disapproval. It would help to distinguish HN from other driveby, populist moderated forums.