Saying that HN is social media is like saying that a taco is a sandwich.
- Barrier to entry is higher and participation is tiered by karma
- Moderation and community participation guidelines are heavier-handed and more defined
- You can't embed media or have a profile picture
- There's virtually no advertising anywhere
- You can't delete posts after a few hours which means no way to nuke your presence after the fact
- No hashtags
- Far less algorithmic manipulation of user attention (infinite scrolling, per-user algorithmic feed, etc)
- Encouragement of longer-form discussion because of a lack of (at this point historical, from what I understand) character limits on posts
- Likes/upvote counts aren't visible to other users
- No official app with telemetry and push notifications; in fact, no notifications _period_ for things like replies
- No friend or follow mechanism
My taco comment stands. Both a sandwich and a taco comprise flat, oblong starches with ingredients in the middle. One or two people have called them the same. In practice virtually nobody would confuse the two or substitute one for the other. People are migrating from Xitter to Bluesky but almost none are migrating to HN.
I think there are two central criteria for some interaction-based online system to be called 'social media': follows, and DMs.
Hacker News has neither of these things, so it isn't social media. YMMV.