How does HN do this community?

My take: Any community is shaped by the intentions and attitudes of the members it attracts (and the ones it doesn't kick out).

This sort of social orderliness (encoded in "netiquette") was much more common pre-mass social media and has since widely regressed.

Welcome to this corner where net culture sort of survived. Nurture it, and see the guidelines/FAQ at https://news.ycombinator.com/newsguidelines.html and https://news.ycombinator.com/newsfaq.html

I think it helps that the HN userbase is primarily smart people who don't take kindly to gratuitous obnoxiousness and trolling. Most of the moderation is done by the community itself: cause trouble, and you get downvoted. The really egregious ones might get a response from mods.

I've noticed something similar on Ars Technica: again, you have a userbase of intelligent professionals, many of whom are long-term regulars. It's a culture that's naturally troll-resistant.

I think building this sort of culture on social media is a lot harder, because social media sites are typically focused on the exact opposite qualities: reflexive, drive-by responses; transient users who have no real investment in the community; and, overall, a userbase that's steeped in pervasive, unchecked toxicity and has started to enjoy it.

I cannot understand how HN did this with almost no "community guidelines"

I would probably word it as simple to follow guidelines and adding to that is a remarkable moderator that is mostly hands-off. There are also many people that have been here long enough to flag the topics they know will descend into chaos most of the time. But that is just my take, there is probably more to it.

It helps having Dan G. as moderator.