Follow on a non-Actor object

[jaywink]

There is some confusion in the ActivityPub specification on what a Follow can be made towards.

The C2S part says "The Follow activity is used to subscribe to the activities of another actor."

https://www.w3.org/TR/activitypub/#follow-activity-outbox

This seems wrong since IMHO it should be a perfectly fine use case to Follow { Note } for example which correlates directly to the Diaspora protocol Participation (https://diaspora.github.io/diaspora_federation/entities/participation.html) which is an important mechanism to subscribe for follow-ups or updates.

This discussion came up in the ForgeFed specification building on top of ActivityPub and thinking whether an Issue also needs to be an actor.

Forum link: https://talk.feneas.org/t/following-non-actors/159