Sure, that’s not the point at all. But wouldn’t it be great if the knitting community (for example) on beehaw.org, lemmy.ml, lemmy.world and feddit.de would be merged for me into one entity for a better browsing experience? And people wouldn’t post the same breaking news 3 times and the cross-posts always showed up 3 times in my timeline? (And sometimes it’s the same 30 people anyways that are subscribed to all of them so the cross-posting doesn’t add anything?)

I currently don’t have a good idea for a UI design for that. But I think a feature like that would add to federated platforms (if done right.) But nobody said you’re not allowed or it’s bad to open a dozen communities with the same name and topic on different servers. That’s perfectly alright. In the real world we also sometimes discuss the same topic with different people at different locations.