Shouldn't the behavior for "Send Emails for Private Posts" default to or least have an option to be based upon the "read_private_posts" capability in wordpress?
This would restrict emails for private posts to go out only to those who already have the right to see private posts already and restrict everyone else.
Thanks for the great plugin.
PS, I've been looking over the code and it looks as though the fix for this would be more than a one-liner. I understand if you don't want to do this.