Are you not posting here?
1. HN is not a place where I seek "likes," karma (I know some do though), or share gifs of cats. Since there is karma and some sort of static identity attached to comments, though, I suppose it could be considered a social site to some. OTOH, I do not hold a Swedish passport, and do not plan to travel to Sweden, so tying my passport or other ID to my identity here would not be obvious, unless you count the NSA or whoever having the ability to tie my real name to this account.
2. I doubt HN is on the DHS list of 'social media sites' with Facebook, Twitter, Instagram, Snapchat, and whatever other sites you kids are using these days.
P.S. Please don't misunderstand me: I love funny cat gifs. It is the main reason to allow the internet to continue to exist.
P.P.S. Yes, the above P.S. was included solely to influence border security when they crack my laptop / phone and find HN on my bookmarked sites with my login credentials saved and start scrolling through my comments here. Fortunately, I self-censor to avoid losing too much karma with any single comment, which should keep me safely in the mainstream of contemporary public mores and avoid arousing suspicion.
In what way do you find it is not social media, or maybe I should ask how narrow is your definition of social media?
I tried to find how exactly DHS defines "social media" because that is actually what is relevant to this discussion, but I was unable. I think someone had posted their definition in one of the other threads on this topic, if you want to try to find it yourself.
Feel free to read through Wikipedia's article: https://en.wikipedia.org/wiki/Social_media
I enjoy getting older. It spares me a lot of drama.