@evan Yes, perhaps I could have phrased the original question better.
My thinking was, currently, a follower can reply to a followers-only post, with a followers-only reply.
So their followers can reply back to you, without seeing the original post, potentially deducing and further exposing personal information contained in the original post.
This is a dilemma I myself have sometimes, when I see a followers-only post. Sometimes it just makes sense for me to reply directly, eg. health status updates.
If I replied with a followers-only post saying "good luck with the heart surgery", all my followers will deduce that Alice is having a heart surgery.