Email notifications originating from a share operation are sent with “From” address beeing the system’s email and the name in front indicates that it is beeing sent by the system on “behalf of” giving the full name of the user originating the share. In addition, there is a “Reply to” header giving the name and email address of the originating user. Any reply from the addresse will go to the right place.
By comparison, invites from the Talk app are sent with the full name of the user originating the invite, but with the system’s email and no “Reply to” header. Should the addressee have to contact the host, there is not direct way to do so in the invite email.
It would be most desirable that invites from the Talk app be done using the same approach as share notifications.