There’s also Mastodon, a Twitter-like service that currently Kbin users can interact with (but not Lemmy).

They can interact with us though, and then we can interact back. We can’t really “post” there, but if a mastodonian makes a post in a Lemmy community, us lemmings can see it, and then we can reply to them. But we can’t do twitter style posts on their forum

The biggest telltale sign you’re talking to a mastodonian rather than a lemming is that you’ll see them @ everybody in the entire thread in every single reply, since that’s how replies start on twitter and mastodon. I’ve never actually received a notification for the @'s, I think it’s functionally closer to just linking to your user profile than an actual mention, but once you get deep in a thread you’ll see every comment starting with 60 different @'s.