I'm not sure there's an awareness the effect a down vote can have on someone new here. I remember when I made a comment after joining and it got a down vote. I didn't comment for about 6 months.

The fact that down votes are silent makes things worse. Great, you've been down voted. Why? Ask why, down vote again. It's almost a recipe for gradual shaping to conformity of group opinion for anyone who wants to participate here. It can then come across as say these things, don't say these things and you'll be sailing.

I don't know, perhaps an explanatory comment should be encouraged so that real education happens. Otherwise its almost Pavlovian in nature, especially for the less confident and highly anxious.

That's fine. I think most of the HN community disagrees with him on that.

Given the way HN is designed (comments are ranked, low scores get grayed out, user karma scores are visible) if people downvote to express disagreement it would worsen the experience of reading comments, and, I suspect, the overall conversation.