Stub issue for me to flesh out later, just wanna get some ideas down:
Use "replies" collection of OP as source of truth for approved replies (will help mitigate issue of replies from non-interaction-policy-enabled instances getting rejected).
Distribute Accept more widely than just to the Acceptee, use Accepts a bit like boosts (go dereference the Accepted status).
Stub issue for me to flesh out later, just wanna get some ideas down: