> It is not generally the practice to comment to explain downvotes, and, IMO -- especially given the absence of collapsed threads on HN, but even if it were present -- it would defeat the point of downvoting and decrease the signal-to-noise ratio to do so, as then meta-discussion of the problem with posts would take more real estate, at the expense of the worthwhile discussion of the topic at hand.
I am not suggesting that every single downvote warrants an explanation. I thought that was obvious. But if you look at the two extremes:
* No downvote is ever expanded on in a comment by the downvoter. The site rules themselves will explain some of the downvotes. However, alone they do a poor job of encapsulating what this community considers productive and unproductive discussion. We usually don't know why downvotes are happening. Nothing improves unless mods take direct action to make it happen, as this community has no mechanism for self-regulation.
* Every downvote is explained. I gather you believe this is the worse of the two extremes and I agree. The forum disappears up its own asshole in endless boring meta-discussion and everyone leaves.
Downvotes should be explained sometimes. My one-in-ten figure from before was a total guess. I haven't harvested any data and I don't have any spreadsheets, but I too often see greyed-out posts that I can't for the life of me figure out why they were downvoted. As in, even if I approach it with an unusually high degree of cynicism I still can't guess at a reason. It's gotten to the point that if I see a grey post I'll just automatically upvote it even if I don't read it. I encourage others to do the same.
It is not generally the practice to comment to explain downvotes, and, IMO -- especially given the absence of collapsed threads on HN, but even if it were present -- it would defeat the point of downvoting and decrease the signal-to-noise ratio to do so, as then meta-discussion of the problem with posts would take more real estate, at the expense of the worthwhile discussion of the topic at hand.
> But less than one in ten heavily-downvoted posts that I read, has a reply to indicate why that post was downvoted. I feel that number is low.
I actually feel that that number is too high. If a comment is worth responding to, its probably not worth downvoting, and if it ought to be downvoted, responding is counterproductive.
> Like I said, it's as though readers need to be "protected" from reading your post (by making it harder to read)
Well, yes, the whole point of moderation, community or otherwise, is to suppress content that is outside of what is desired for the forum so as to maintain the character that is intended for the forum.
Put bluntly, censorship based on the community perception of how well posts align with the ideals expressed in the guidelines is the whole purpose of having downvotes. It is, by design, fairly soft censorship that doesn't (through downvotes alone) actually make the content unavailable, but it is exactly to protect the community from the unwanted content interfering with the wanted content.
> which is patronizing to readers and a bit harsh to the author of the post
I don't think its patronizing to the reader to hold out a representation of what the purpose of the forum is and to minimize the visibiity of content that the community has found to be out of line with that purpose. Nor do I find the manner in which HN does it "harsh to the author", despite myself having had many comments go gray -- though far fewer stay there.
In fact, I've often found that a comment going gray triggers my own review and reconsideration, and an edit which makes me happier with the comment. Or results in me deleting a comment which on reflection I realize was ill-considered.
> Greying-out earnest comments merely because they are useless (and remember that's in the best case) is over the line because the consequence of a false positive is too high and the threshold for it to happen (again - one downvote) is too low
I disagree. While its true that a slight greying that lets you know that a comment has been downvoted occurs at a net of one downvote, I don't see that as a "too high" consequence of a false positive. The slight greying at that level doesn't impair readability, and if anything draws more attention to the post. Its only at higher levels of downvoting that there is a substantial negative consequence.
I fail to see the harm you are concerned about here. Perhaps its just being around a long time in online forums, but I think the consequences of no moderation (and voting that doesn't actually reduce the visibility of negatively-voted comments at some point is "no moderation" for this purpose), or of relying primarily on centralized moderation rather than community moderations, are much worse than HN's style of community moderation. And while there are different styles of community moderation (e.g., those used at Slashdot or Reddit), I don't see any clear evidence that they produce better results than HN's.