That would discourage the demoralising situation where someone gets downvoted but is left guessing why.
It encourages replying to bad comments which is already a bigger problem than the sting of an unexpounded-upon downvote. 'No receipts required for downvotes' makes HN better.
Strongly disagree. Maybe most people don’t receive feedback. But I believe there is at least a minority that does and can be influenced by feedback. Similar to US politics.
Edit: Notice how I upvoted you rather than downvoted out of disagreement
He doesn't notice that, because votes at the margin are random, and 4 times out of 5 people complaining about voting can just wait and whatever's bothering them will be rectified organically.
The downvoted commenter would still have no way to tell whether the downvote was related to the reply, since those would most often be coming from different users.
Of course, there will be some comments which do not merit a reply (non-substantive contributions or blatant trolling) - but, those comments should be flagged anyway. Maybe count flags as downvotes (if they aren’t already), so you could still downvote reply-less comments by flagging them.