I heard a couple of months back that Threads was joining the Fediverse but didn't actually see anything from Threads in my Mastodon feed until the past couple of days. Nothing bad; it was some posts by Aaron Rupar that somebody was boosting.
There's a debate going right now about whether or not Mastodon instances should federate with Threads. The "for" argument is that if we want Mastodon to be a mainstream social networking option, we can't just shun the single biggest source of potential converts; the "against" argument is that Facebook gonna Facebook and isn't going to moderate abusive posters in line with most Mastodon instances' guidelines. (Plus if you interact privately with Threads members you're giving Facebook access to those private messages.) I'm kind of in "wait and see" mode before I decide where I personally come down on this particular cost/benefit analysis, and anyway I'm not running my own Mastodon instance anyway so it's not like it's my call to make.
(I don't know if the harassment we were talking about on the private board involved anybody from Threads, but I do think that federating with Threads inevitably means that stuff like that is going to happen more often.)
I keep hearing good things about Bluesky (
Scalzi,
Masnick) and evidently Dorsey's no longer on the board, which I consider a mark in its favor. It's still early days for federation, but if independent Bluesky instances start to take off then I may have to give it a look.