However, what I don't see so often is a reason for the downvote that would inform the OP of the undesired behavior and maybe give the opportunity to explain, elaborate, or even apologize. Downvotes seem to be "fire and forget" in nature. I wonder if anyone ever removes a downvote after an exchange with the OP.
That's why I'd like to propose, could we force those who decide to downvote a comment to leave respectful feedback for the OP? Assuming that downvoting is not a way to retaliate against a user but to correct unwelcome behavior, I think that a comment would be much more effective in reaching that goal.
Edit: Autocorrect.
The crux of why I don't comment is almost always the same: I'm not interested in investing my time in debating them. I already know they think their comment is good, I already know I think their comment is (subjectively) bad, I'm not interested in hearing their righteousness in finer detail. If I want to have a discussion with someone on their comment, I will add a comment myself and usually upvote because their commentary invites further discussion which is good.
In short, I look at (subjectively) bad comments the same way I look at spam email. I'm not interested in wasting my time to be convinced by someone else that their content really is good, when for me it clearly isn't. My downvote will hopefully help save others the time the same way spam filters help save time for everyone.
Second, here's someone who leaves a lazy, drive-by comment. It's two words long. It took them five seconds. It has no actual thought, and therefore it's not the kind of comment we want on HN. How long should someone have to spend to be able to downvote it? If it's longer than 5 seconds, that's a problem. That puts the lazy, thoughtless commenter in the advantageous position. So what will happen instead is that users will flag the comment instead of downvoting it, because that's faster (under your proposal).
Even if it's a more worthwhile comment, it can be factually wrong. You may want to downvote it for that reason, but you may not have time (or mental energy) to explain why it's wrong for every such comment that you see. (The explanation is better than a bare downvote, of course, unless someone has already given the explanation.) But a downvote with "factually wrong" (and no explanation/details/evidence) isn't really going to raise the level of discourse much. I mean, it tells the original poster more than a bare downvote does, but not much more.
Even pg acknowledged and agreed long ago that downvotes are/can be used to flag disagreement or dislike for a position. [1]
[1]: unable to find the more substantial comment, but here’s one. https://news.ycombinator.com/item?id=392347
Some people aren't going to behave better just because you asked them to or explained why people downvoted their comment. Especially coming from a random internet stranger, this is usually experienced as an attack, not an attempt to be helpful.
And it's often not actually meant to be genuinely helpful. It often is fairly ugly behavior where someone feels like they can dictate to you how you are allowed to participate.
This means demographic outliers, minority views of any sort (in the sense of "a view not held by most people here") and anyone who has ever been picked on can be bullied, told to get in line and it's your fault you are being attacked.
That's not a path forward towards a better discussion forum.
As things stand currently, if you are willing to soak up the downvotes and you, yourself, follow the rules and are respectful, you can speak your mind and take a stand on unpopular positions, etc.
This is a forum that values rigorous scientific discussion. When social crap becomes more important than being able to state the truth as you understand it and have some hope of meaningful discussion, then HN is dead.
Hurt feelings about downvotes is social crap.
The culture supports the practice of corrective upvotes. That is sufficient to ameliorate most bad downvotes.
We don't need to actively encourage negative engagement, bullying and an attitude that you are required to get with the program and march to the same tune as everyone else lest a single downvotes lead to a pile on of ridiculous and pointless drama.
Anyway, there are a couple of problems that come to mind with the proposal.
1. If someone says something that draws a lot of downvotes there is going to be a lot of redundancy in the required comments. Do we really need or want the worst comments to have dozens of replies all giving the same reason for downvoting?
2. It will attract trolls who enjoy posting downvote worthy things for the enjoyment of knowing that people have to waste time commenting in order to downvote them.
You could maybe fix these problems by having an option to instead of writing a new comment explaining your downvote cite an existing comment.
Also the suggestion would balloon the number of comments and make the thread even harder to read
When I was a kid people called me names, kicked me in the face, etc. Many of the most successful people in history (say Benjamin Disraeli) took the worst kind of crap from people and spun it into gold. Complaining about it is going to get you more downvotes at best.