My impression so far largely aligns what the author is saying. I see a lot of comments along the lines of "so this is the internet, it's no worse than other communities" and such. The weird thing is that response seems to come with a sort of rejection of what the author's point is. It's no worse, but it's not a lot better either. I've noticed that there is definitely a gap between the stated goals of HN (which I read carefully when I finally decided to create an account) and the reality of how people interact. There are plenty of rude comments and responses that do not follow the guidelines.
In case it's of interest, my education is software engineering. I feel that I had a similar experience to the author's. For a little while, I had too much of a know-it-all attitude and that sometimes lead me to being rude and dismissive of others. In my experience, that's really common with engineers. I imagine in other highly educated profession5s too.
I'm not intending to complain, just sharing my viewpoint as another person out there looking here. I think this community can do better and very often does not live up to its goals. But, despite that, I still find a lot of value here and I try to bring my own positivity and ignore the toxicity.