What I think HN has taught me is that for any X you feel strongly about, if you actually were in a community that was evenly divided about X, you wouldn't know it. Instead, you would feel yourself surrounded by enemies. Why? Because we notice what we dislike more strongly than what we like. We remember painful experiences more than pleasurable ones, and it's painful to read comments opposing our strongly held X's. So people feel like the community is biased whether it is or not. Unfortunately they feel this the most about the most divisive topics.

I arrived at this view because I have a different perspective than most users. It's my job to monitor the site overall, plus pay attention to the complaints people make about it. From such a position one quickly notices how many complaints about HN contradict each another. For example, for any political X, some people are certain that HN is overwhelmingly X. But those claims can't all be true, so there has to be some distortion at work here.

Edit: here's an example I just ran across: https://news.ycombinator.com/item?id=11990458. (I'm not mentioning that to single one user out; it's a common phenomenon, and this is just the first example I saw after writing the above.)