There’s another candidate-solution worth considering:
Votes could put the “Server Actor” in the "actor" property of a Vote activity, but a pseudonym in the "attributedTo" property. Note a detailed proposal for doing server-pseudonymized-yet-stable pseudonyms for moderation reports here. Insofar as “Instance Actors” are a thing, and maybe they aren’t in the Foraverse, I think this is actually a cleaner modeling; it’s worth noting that in Emelia’s use case (distributed moderation records), it’s also important to get updates when a pseudonym’s controller deactivates, or to be able to moderate/filter/judge on both an individual-actor and a domain/server/collective level…