Hello. Hopefully you won't mind if I jump into the silence and offer a live test :-)
Here's my setup:
Virgin install of WordPress 3.5.1
No plugins except for cbnet Multi Author Comment Notification 2.2.1
Twenty Eleven theme 1.5
Only users are the admin and 2 Authors
Everything else is default except for Discussions page:
E-mail me whenever:
[ ] Anyone posts a comment
[ ] A comment is held for moderation
[x] Send comment notification emails to all Authors
Additional Emails defaults to Array (default value after install)
[x] Send notification emails for comments from registered users
[x] Send notification emails for comments held for Moderation
My understanding of the plugin is that with these settings, any comments on the post (Hello World) should email all Authors whether the comment author has previously approved comments or not. I've tested by commenting from the admin user and as an anonymous visitor. No email is sent unless I check those two boxes to send email notifications to the blog owner... which I don't want.
I also tested using the User - Edit - setting
Comment Email Notification [x] Receive email notification of comments to all posts, regardless of post author
But again, no emails were sent to either of the two users selected in this manner.
I have sent WordPress location/user/pass details via your websites' contact form.