The best social media experience I ever had was a webserver that a bunch of teenagers ran for ourselves and our friends on a computer in the multimedia room of the democratic school we went to in the early 2000s. (It also ran IRC and email.) Everyone with an account had websites to do with as we would -- a few weblogs, all in dialogue with one another; some poetry; a predictably high number of impenetrable inside jokes -- and there was a hub page to direct you to them, which was simple and silly but quite pretty, really, owing mostly to a lilac-blue background colour (#AFAFFF) that @cola probably picked. Most of us had root access and could edit that page, which we mainly did to periodically update the top banner image with a new nethack high score. It had a URL that looked like gibberish and was rarely linked to, so it was difficult to stumble upon, but occasionally a stranger managed it and left confused messages on the guestbook, and I liked to imagine how weird and interesting it would be to find it unexpectedly like that. It helped me have an ongoing faith that the internet was full of little enclaves just as weird that I hadn't found yet.
Cohost is nothing like that architecturally; I was mainly expecting it to remind me of livejournal. But there's also a vibe in a lot of the stuff I'm seeing on here, a low stakes playfulness with HTML or whatever markup we're actually using these days, that is pleasantly familiar from those days on that site.