NotifyActor - cc to person answering ticket causes extra mail

I have:

Set($NotifyActor, 1);

set in my When a user here is responding to a ticket, and
puts her own email address in the CC: field, she gets one mail with no To:
field and her address in the CC: field, and another mail with her address in
the To: field and no CC:. It’s just a cosmetic problem, since the mail does
go. Is this expected behavior, since I have the notification override above?
i.e. Does anyone else see this?