Private item notification should be handled different, most notably to avoid mails getting sent to private list.

One easy option would be to set a list of address to remove from notification of private item and another of address to add.
The point would be to avoid having one more field to fill for notification. The drawback is obvious, it is less flexible.

I'm not sure what would be the best way, if we need that flexibility or not. That's why I dot not asap implement this feature, I'd like to receive some input, especially if the above proposal if not satisfactory in your opinion.