It doesn't matter how infrequent the comments we dislike are relative to the whole. What matters is the absolute number of them that an individual reader encounters. If it's more than some threshold value N, they will conclude that the entire place is hostile, even if the hostile comments are a tiny minority. At a psychological and even a biological level, that makes sense: once a place has generated N painful experiences, it's dangerous. Percentage of the total is irrelevant. Indeed, it makes a place even more dangerous if most experiences there are pleasurable, since one will be inclined to stay—exposing oneself to future smacks—and to let one's guard down, making the next smack even more painful. We all have a version of this, and though N may vary per person, I bet it's lower than most of us would predict.
This phenomenon has some interesting consequences. One is that it enables you to guess with high confidence what someone's views on a topic are, based on how strongly they believe HN (or whatever forum) is biased against them. Maybe it is, maybe it isn't, but the feeling that it is shows what they find painful and therefore what they disagree with. Also, the intensity of the belief in bias grows with the intensity of their view on the topic. That is, the more passionately you believe X, the more pain an anti-X comment causes, the more strongly you will believe that the forum is anti-X.
Another consequence is that the closer a forum gets to being unbiased, the more all sides will believe that it's actually hostile to their views. That seems weird in the wild, but it's simple: the more diverse the comment stream is, the more likely all sides are to notice disagreeable comments and thus receive painful impressions.
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https://hn.algolia.com/?dateRange=all&page=0&prefix=false&qu...
It's always a joy reading your thoughts on moderation and communities in general--keep up the awesome work!