I understand why it can be beneficial but it brings so many potential complications and issues that I think on balance it would be worth trying to address it somehow, maybe through codes of conduct, policy and enhanced search and validation at the point a community is created. Wouldn't be perfect by any means, and I don't think it should be a requirement to stop duplicate communities - but as an example to prevent issues with mergers and fractured user bases, with the android community being a recent instance of a disgruntled users where an established community has been shut down and moved to another instance with no way for the existing community to reclaim their space.

There are potentially issues with community name squatting, duplicate content and cross posting, users missing out on conversation from one instance if they aren't aware of it; and when large companies start to move into the space, there will be communities swallowed up potentially, and the various issues and questions and clashes it causes.

I suspect there are also going to be issues as the site grows with where servers are located and how compliant they are with GDPR and other regulations too.

Even the getting started guide for .world (and others) mention check other instances for duplicate communities first, so it is likely something that needs to be addressed in some form.

It's a really interesting subject that will be fascinating to see how it unfolds over time!