alt Hacker Newssee IMO it isn't. HN is an online community. Same as forums, and BBSs were. I don't think they were social media really - they're online spaces that form around a shared interest, where Facebook etc were originally online spaces that augmented a real world community.
But we're a long way from that now.
> HN is an online community. Same as forums, and BBSs were.
That is the very definition of social media.
"Social media I like" vs. "Social media I don't like" isn't valid categorization.