Geez I gotta find a way to demo this to Fedi people.
So, Ravelry never meant to be a social site AFAIK. They had a handful of "Forums" that were to be online help oriented, dialogue with either the site's developers, or their contracted or volunteer knitting & yarn & pattern experts. Then they added "groups" which included a forum, and some Pages (static info for the Group), few other things AND IT WENT NUTS.
And it has somehow remained the most civilized social network ever.
@julian There's no "main" vs. "sub", other than by default all users join (and can leave) the "Big 6" official Ravelry forums.
Groups are all subject to Ravelry's TOS but can be created by anyone, any topic. There are lots of abandoned or inactive ones, and they could probably do a clean up (but also probably ... don't need to bother?)
Ravelry users belong to as many groups as they want to bother with, under one ID.
It's a unique site. Even if there was no emulating it, it's a case study.