HN mostly reminds me of the Usenet of the late 1980s - which was in a way the social media of its time.
In terms of signal-to-noise ratio and the content focus, you're right. HN is the closest thing to the 80s Usenet community that I've found on the Internet of the current day.
However, Usenet was never social media. You didn't connect with people like you do on social media and 'follow' them. On Usenet you joined discussion fora, which sometimes included the same people across multiple fora, so you would get a sense of the poster and their calibre and quality.
Did Usenet not require any moderation? Or was it simply the barrier for entry that made people behave like the access was a scarce resource? Or what do You think made the period so unique?
Usenet didn't (in general, IIRC) have centralised moderation. Usenet had the famous killfiles, which you maintained and which elided the posts of people you found to be a nuisance.