@trwnh @steve @raucao I am not convinced that there is a problem in the first place.
ActivityPub says the identifier is https://www.w3.org/ns/activitystreams#Public. JSON publishers use full URI. Server implementations that perform JSON-LD processing (e.g. Iceshrimp) also produce full URI, they figured it out. Then, why make a change?
If this issue is purely theoretical, then it must be addressed without changing ActivityPub.