Considering the relative rationality and aversion to groupthink that people on HN seem to have, this seems to me (although I don't have much experience with mod

Considering the relative rationality and aversion to groupthink that people on HN seem to have, this seems to me (although I don't have much experience with moderating online communities) like a generally bad idea. I would expect people to see that Post X has -Y points and desist because the poster doesn't deserve -(Y + 1) karma for the comment. Hiding this information from the downvoter makes him do something he might otherwise not do, and I would expect this effect to be far greater on a site like HN than the drive to "pile onto a downvote frenzy."