@LibertyLizard @technology It always has. They both speak ActivityPub.

The UX can be awkward though. As an example, I had to add the community tag to this comment manually, as it won't federate to lemmy.world otherwise. That's because Mastodon doesn't push replies to every server with users participating in a thread, which I think is a design flaw.

To post to Lemmy from Mastodon, just tag a community. You can load any of the fediverse links shown in the default Lemmy web UI in a Mastodon search box and reply to them. You can also follow a community and receive every subsequent post and comment as a boost (this is a bad UX and I don't recommend it), as well as follow Lemmy users, which you can't do in Lemmy itself. You cannot vote on Lemmy posts/comments from Mastodon.

I find tagging an appropriate Lemmy community from my Mastodon posts to be a good experience. You'll see a few of those from my @zaktakespictures account in @birding, and from @zakreviews in @flashlight.

I'm pretty sure Lemmy won't make new toplevel posts out of this in those communities since it's a reply, but I'm going to check just to be sure.