I wonder if the old forum model would work. Instead of these mega-forum-platfroms, there are just small communities with a niche focus at their own URL.
replyI suppose bots could find forums that use the most popular software and still make accounts and spam, but it would be much more obvious and less fruitful for someone to spam deck builders in Vancouver (something I saw often on Digg) on a forum that is focused on aquariums owners in the midwest.
Spammers don't care if it's fruitful - they just run software that finds every forum and spams it. That's why you can block so many by asking "is an elephant big or small?" on the sign-up form.
replyOld forums still exist and work just fine without any CEOs pontificating about "community".
replyI'm on plenty of niche interest boards built on PHPbb, Xenforo and Discourse. Chronologically ordered discussions, RSS support, no algorithmic "For You" bullshit.
Build it and they will come.