That's a property of some kinds of social media. Not a definition or negation of.

The most amusing thing is that discussions on reddit, tumblr, x, etc include the very same kind of denials that gp comment is eliciting regarding those sites being social media.

Social media includes content sharing, discussions, and echo chambers, all of which are present here in abundance. Certain content gets promoted over others, and each site assumes see itself above others.