or maybe at least the posts wouldn’t be replicated, but there would only be one community, and when you visit it, posts for the community are downloaded from your primary instance, as well as other instances based on some configuration that makes sense.
I feel like if you’re okay with limiting it to communities with the exact same name, that this could be handled on the front end by app or web developers. I have seen some of the arguments about how it would be a lot of work for fairly little benefit on the back-end and I’m sympathetic, but “faking it” from a UI perspective shouldn’t be too terribly difficult (said the non-coder).
i think enough people want the feature that the benefit would be worth it
you actually wouldn’t have to limit it to exact same name if you’re making a front-end thing, if you allow for the user to configure their “merged communities”