@evan Given all the complexities and real and potential vectors of abuse, maybe replies to followers-only posts should be forced to be private mentions?
Sometimes people share personal things using followers-only visibility, and replying directly without exposing private details seems the most appropriate.
Eg. not announcing "Hope you'll recover from the diarrhea soon, Bob!" to potentially thousands of strangers, or even people who do know Bob, but Bob was not addressing in his post.