Howdy folks. I just had a user bring up the same issue (which led me to this thread here).
She’s got her settings set to receive an email for every post and she has muted a couple of people but are still getting emails from them when they post.
(I’m also trying reproduce this myself with her exact settings but it may take a couple of days for me to be able to reproduce it.)
In case this helps, I was just able to reproduce the bug that our user reported. Steps: Mute a user and you still get the individual emails when they post.