Having some moderation functionality embedded at the ActivityPub layer would definitely help in streamlining the moderation process between two instances. Hopefully you'll be able to add functionality that useful the developers of Fediverse software would be incentivized to interact with the standard.
Something we've been doing at Neondystopia.world that the culture of the Fediverse could benefit from is comparing our rules against those of the instance from which a report originated. That way, we can determine whether a violation occurred and inform what our next course of action would be to address the issue.
By providing a way for the staff of instances to communicate directly between each other and expose that communication to the appropriate designated roles, violations could be discussed in an open and transparent manner and facilitate closer cooperation between instances in doing so. Helping shape a better culture where defederation and frivolous reports aren't the first course of taken action.
That said, when you start considering how two instances can communicate with each other in a manner that respects designated roles, you end up moving beyond the scope of a protocol into feature implementation for Fediverse software.
@thisismissem@activitypub.space