@Gargron like Google+ Collections, you post to a Collection and people can follow a specific Collection to receive just those posts. or they can follow you but unfollow one of your Collections, to not receive those posts.

if that sounds confusing it's basically just categories on wordpress, or those access lists on facebook, or what people rn make multiple accounts for

i think as:streams is this but following non-actors is still kinda undefined so it'd probably have to be receiver-side filters