@helge These two protocols may seem very different, but it was discovered that they are fundamentally the same. This is what FEP-fe34 really is: a Grand Unified Theory of Fediverse.
Same-origin policy applies to both HTTP URLs and DID-based identifiers. In the first case authority is derived from a DNS name, and in the second case it is derived from a DID, but otherwise the logic of authentication is similar.
Yes, servers still need to support DIDs and integrity proofs in order to understand what is going on, but mechanisms like reply controls can be designed in a way that works with both kinds of authorities.
For example, Conversation Containers are compatible with FEP-fe34, so I expect them to work in nomadic Fediverse too.