All of the public methods exposed by an actor could be considered its location-agnostic API, so it could be interesting to consider a reverse rule for them - instead of requiring all of the accessible (in a use-site sense) methods be annotated as distributed, consider them distributed by default and allow specifying local for the ones that could only be reached specifically on a "local" version of the actor.
If method has to be annotated as public e.g. to allow an actor to satisfy protocol requirement it should also be annotated as local to avoid publishing it as part of a location-agnostic actor interface.
I think this brings semantics closer to nonisolated of non-distributed actors and allows to clearly define that all of the properties of a distributed actor are implicitly local as well as all of its "internal" methods which are not part of an actor interface and cannot be accessed from its instance.