Currently it's missing exactly the federation component, so people on Mastodon can't interact with it yet, but it's getting there. :)
On prismo I haven't seen any work being done in a while (more than half a year according to the repo you linked :D). I think the dev got a bit discouraged after his instance had a data loss problem. It used to be at https://prismo.xyz but seems to be down.
One which is pretty active (development wise) is https://dev.lemmy.ml. But they don't have federation yet either.
People with multiple accounts with the same name/icons often call these accounts "alts" .. and it's kinda easy to create a fake alt for someone (although KeyBase supports mastodon so you can kinda setup your "identity" that way; although each individual server has to be added to the big Keybase list).
It's really more like old IRC/AOL chat rooms .. with threads.