> If the old server is offline or unwilling, you cannot move - Your old toots and interactions will still be tied to the old address, so you leave those behind.

> If the old server is offline or unwilling, you cannot move - Your old toots and interactions will still be tied to the old address, so you leave those behind. This is just like any other system that combine content delivery and identity on the same channel (e.g. web sites). Even if those 2 were separate, if your centralized identity provider is down, there is no way to update clients that depend on it, or to safely attest a new identity. Allowing unverified servers to claim an identity or kick off a migration is a recipe for widespread hacking.