Fedify maintainer here. Agreed on the key handling. The manual warns about this too: Fedify currently has no workflow for rotating the DID’s key or moving an actor to another DID. One distinction for anyone experimenting: the gateway keys that sign HTTP requests on the actor’s behalf are separate server keys, listed in the DID-signed actor document, so replacing them doesn’t change the identity. The DID key is different. A did:key identifier encodes the public key itself, so a new key means a new DID.

On rotation, there’s no concrete design for #413 yet. I expect it to become an umbrella issue, with key rotation as one of its sub-issues. Since a did:key can’t rotate, that will probably mean supporting another DID method or adding some kind of migration mechanism.