I really find this an useful feature. Currently, the plugin is simply filtering the ; or , chars if I type two emails in the address field (in the format email@example.com;firstname.lastname@example.org). It should ignore the ; or , separator and that would allow to receive a copy of the backups when the website has several admins, or an admin and an owner.
It's just about ignoring a character which cannot harm the system. It's an easy one :)
Hope others second this and you can implement it soon.