From a definition standpoint, hn is a social media site. From a legislation standpoint, it's not nearly popular (infamous?) enough to legislate (the mentioned sites have had enough negative coverage to manufacturer consent for this invasion of privacy: cyber bullying, destructive challenges, etc.)
When it is, and when your local government becomes sufficiently captured by the user surveillance industrial complex, you will need real world verification here.
Social media typically implies a website where users are sharing self-created content. If a website with comments counts a social media, than all web2.0 is social media and there's practically no distinction between the web and social media.
A blog that has a comments section is primarily still a blog, it just has a secondary social media feature attached.
In the case of HN, most people are here for the comments section and frequently don't even read the article, so it's primarily a social media site with a news aggregator feature.
When it is, and when your local government becomes sufficiently captured by the user surveillance industrial complex, you will need real world verification here.