I’m still sticking with Mastodon, as I mentioned last spring. Twitter is down to reply-only. And I’ve deleted (mostly) my Facebook account, though I’m pretty sure FB resurrected it when someone tried to log into it.
My biggest issue with Masto, technologically, is that it’s a pretty heavyweight critter to run for a single-user instance. So I’ve been playing around with the idea of minimum-viable instance, more as a way to wrap my head around the standards it uses than as an attempt at building a usable product. (But if that happens anyway, cool.) I think the most worthwhile thing I could end up with is a coherent set of documentation for the standards, though, because for instance as far as I can tell the Salmon protocol’s specification only lives in a Wayback machine archive of a Google Code site (Salmon spec and magic-signature spec).