>I don't include HN in the same "social media" as twitter/facebook/Instagram
I don't either -- HN is the same category as Reddit which is much worse to me.
>Over there most people use their real identities and it seems they take everything very personal as a result. Here people are just nicknames in a comment section
There are plenty of people taking things personally here, all the time, and if you stick around you'll notice that a good number of them either use their real names as a handle or have it in their profile. And there are "celebrities" here just like there are on Reddit, except here it's usually tied to some high-ranking position at a company. For instance, the CEO of Matrix has many comments under the username Arathorn in almost every single post about Matrix.
>I don't see many negatives of sites like HN
Tree-style nearly-endless commentary combined with an algorithmic ranking of "top" stories that may have a big payoff if I just press refresh one more time turns out to be way, way more addictive than "traditional" social media, at least for me. Twitter never hooked me, and I kicked Facebook a decade ago, but even after forcing myself to use a privacy frontend for Reddit and never, ever logging in, I'm still addicted. I spend hours a day scrolling, and resolve to quit, and then go back.
I do the same thing here. It's so bad that I consider HN and Reddit to be as addictive as video poker.