Practically, I myself have experienced several fragmented communities about the same topic with similar ethos. This was not a healthy separation based on different norms. It was simple, ineffective fragmentation. Or, at least the ethos and norms differences wasn't clear.

[–] SorteKanin@feddit.dk 4 points 2 days ago

I feel like it is just a matter of time before either:

The fragmented communities develop more and become distinct, so that they are more unique and shouldn't merge.
One of the communities becomes the more popular "default" option, and the other becomes less active as people gather in the more popular one.

Even if that doesn't happen, redundancy isn't bad. We've seen how hard it is to migrate when there's only 1 real option and that option disappears or goes bad for some reason (i.e. reddit). If there was another fairly active community with the same focus, that would make it easier to keep going. That's part of why decentralization is good.