Oooh, okay. So if I subscribe to !startrek, then kbin would store that data, and I would be able to point everyone to !startrek and we'd all be able to pick up where we left off? Still an issue of getting users to change where they're posting to, but that's better than I thought, at least.
Also, I imagine the problem with how difficult it is to migrate away from commercial centralized services is that it's hard to spin up a new version of that site with the code and database. Being quick to spin up a new kbin instance or Lemmy instance helps immensely, though the issue of directing the users to those new instances would be just as difficult.