I can see that I can follow Lemmy communities from Mastodon (just tried it out with a handful of communities), but I don’t see a way to have it work the other way.
There’s a few lovely people on Mastodon that post things I’d love to see pop up in my Lemmy feed - like @Curator@mastodon.art, for example. But I can’t figure out how to follow them from here?
Modelling tags as communities actually sounds like a good idea though. But you wouldn’t want to namespace them by instance, hmm. I guess they could just have their own namespace as a pseudo-instance.