We’re hitting the length limit for posts, so I’ll add here a stub of a last section of the implementers’ guide on how to improve ActivityPub as suggested earlier by @Sebastian:
Improving ActivityPub
Aided by a culture of collaboration among Fediverse advocates and participants, there is ongoing work to improve both the ActivityPub specification and interoperability among different ActivityPub implementations. Initiatives like FediConf, Feneas, and the ActivityPub forum on Activitypub.Rocks are great places to connect with other implementers and help move things forward.