My problem was that I have to subscribe to an instance in order to see its posts. If I'm subscribed to !startrek@startrek.website, and they decide to shut off access to the Fediverse for whatever reason, all the content would be gone to me here on kbin, right? Also: I would need to subscribe to a new Star Trek community, because I could no longer connect with the old community? What do you mean by, "the content would remain available to both"? If they shut off the Fediverse, or blacklist my instance, wouldn't that mean I no longer have access to their content, even old content that I posted?
And yeah, when I say, "migrate," I mean, "getting people to subscribe to a different instance, because the one they were using turned evil/shut down/disconnected from the Fediverse, etc." Wouldn't those scenarios still mandate action by the users in order to find a new community, and thus equate to migration? Just because a new instance has the same number of users that can post there, doesn't mean there will be the same number of users actively posting there. They will still be using the old instance, and it will take work to get them to start posting to the new instance. That's my point. From my understanding, the Fediverse decentralizes user accounts, but it doesn't decentralize content, and that's where I'm running into my expectations/wishlist issues.
Technically can't they do that even now?