The absolute key feature is the domain experts, not the karma. Any time any subject comes up, someone appears that knows everything about the subject and lives in the field. It’s the single best thing about HN by a million miles.
I remember a guy that had millions just because on any reddit AMA asked "tits or ass?"
You're right about reddit karma though. One of the good things about HN is that throwaway joke posts like that are downvoted/flagged/otherwise discouraged. I can guess the top comment for any given Reddit comment section with like 90% accuracy just because it's going to be the most obvious joke possible based on the submission title, and Reddit users love upvoting those for some reason.
https://fandomwire.com/karma-slapped-ea-with-the-most-downvo... (there are probably better articles about it out there, I quit reddit a long time ago)
<1: Troll
<10: Throwaway
<60: Troll
<300: Probably a throwaway. Quality varies widely.
>500, <1000: Normal people
>1000, account less than 6 months old: Redditor, all content will be political or occasionally about Linux, most comments will be inflammatory.
<1000, >10,000, account less than 5 years old: Mostly normal users. Quality isn’t generally great.
<10,000, >30,000, account 10+ years old: Usually the best quality posts; karma and age suggest consistent contributions overtime without any of the personality disorders that go with being terminally online.
>100,000, account <5 years old: Redditor, all content will be political or occasionally about Linux, most comments will be inflammatory. Lots of flagged submissions about US politics.
>100,000, 10+ years old: Domain knowledge expert. Usually an older user with enough of a reputation that a subset of users know the user’s real identity. Will occasionally post absolutely unhinged comments.