If Alice makes a followers-only post, and Bob replies to it, to whom should Bob's reply be visible?

#EvanPoll #poll

Alice's followers
72.4%
Bob's followers
4.4%
Both Alice's and Bob's followers
18.8%
Other (please specify)
4.4%
Poll ended at .
I'm not speaking about any particular two people but if you need it please consider @alice_watson and @bobwyman as the characters in this story.
@evan can the reply be marked followers only from Bob's side?
@maj yes, that's the default for Mastodon, I think. It is only visible to Bob's followers.
@evan I'm going to need a diagram! This is like set theory.

@evan @maj That’s what the state is today, but you asked what the visibility *should be*.

It seems that replies to a followers-only post *should be* visible to anybody who can see the original post.