I believe more and more people will escape to lemmy sooner or later, and I already see 3 different communities for the same thing (selfhosted) here on lemmy. Time will tell which one will be the most active, but lets assume all of them will be equally active and the desire emerges to combine the two communities about the same thing, is that something possible or intended to be possible with federated services?
As another pointed out, that already happens. It’s even preferable, to some. For example, I had a programming multi reddit with JavaScript and several more focused JS related subs in it. Seeing the same link or topic in multiple subs often let me get more viewpoints to consider. Outside of the web, journalism outfits all publish Associated Press articles. If you follow multiple news outlets you’ll see the same story that way as well.
To me, it’s just natural.