Well said. This irrationality cuts both ways. It's very common for people to jump to "I suspect people are downvoting simply because they disagree", but I think there are fewer people doing this
irrationally on HN than one might be tempted to believe, especially if one's own comment is downvoted, and especially if one is acquainted with the rest of the internet. I think
most people here downvote because they reasonably believe a comment is low value, written in bad faith, or contains misinformation, even if that is informed by bias. Bias is unavoidable and natural, but I think on HN it tends to be less severe and less poisonous/tribal.
This is all pretty subjective, but in the end I think downvoting is broadly useful in most communities. If I find myself being downvoted a lot in some community, I probably don't fit in there. That's fine - there are so many communities, and they all deserve to exist, and they can't all be for everybody, and when they have no capacity for self-moderation, their content inevitably becomes very low value (though potentially high in humor). The biggest problem with downvoting is that it tends to push people toward this oppressed, self-pitying, underdog mentality where people will start to act superior for the simple fact of having been downvoted, and attempt to rally others to identify with them and take their side against the "thought-policing elites".