It's interesting how this issue is new (in my experience) to the Fediverse with Lemmy. With Mastodon you essentially have this uniqueness functionality built in. Because a person isn't likely to post content to multiple accounts under the same persona. Instead someone will choose their instance and username and that's where you can find them. Sure a user might have multiple accounts but I think usually it's to separate multiple online personas.

I think there is use in having same named communities in Lemmy on different servers because they could be for different purposes.

But I can see multiple duplicate communities with the same purpose being on different servers causing fragmentation. Maybe we'll end up with popularity wars and eventually one duplicate community will give way to the other?

Is this similar to the global DNS network? There would need to be a protocol to exchange and keep the list up to date

This would be excellent if done right. What I am curious about is, where this will be implemented? On the protocol level in activity pub or with each GUI (mastodon, pixelfed, lemmy, kbin etc) need to individually implemented it?

not sure that solution is a good one for this environment. I'm new but from what i've seen the concept of moderation is different and your solution is trying to engineer a reddit-like moderation design to an architecture that is fundamentally not reddit-like. Moderation here is at the instance level, not the community level.

How does that not defeat the entire purpose? You're suggesting one global 'sublemmy', as it were, with one global team of moderators. How is that in any way different or better than what we just left behind?

I can't form an opinion right now.
If all similar communities appeared combined into a single community I'd still be likely to want to still filter out sources.
But at the same time sometimes a place to see them all together sounds appealing.
It seems that I want both, but probably what we have now is the most flexible, forcing less limitations.