I think if you expand it that much, the term's useless. HN lacks a couple things that I'd consider necessary for something to for-sure qualify as "social media"

I think if you expand it that much, the term's useless. HN lacks a couple things that I'd consider necessary for something to for-sure qualify as "social media": a personalized queue/feed, and some sort of prominent and heavily-used "follow" action. Those are two distinguishing features of the first things I recall the term ever being applied to—as far as I'm aware, the term was coined for that kind of thing. If the "social network" and actions related to it aren't present or aren't central to the experience, I wouldn't call something social media.