If you enter this in CC field of the comment or reply screen:
Jim will receive the email, Joe won’t. And there will be nothing
whatsoever telling you about the missing email to Joe, because it will
have never been sent. Not even a trace in the database.
I was looking at fixing this, but there is no obvious way to report an
entry error in the Ticket/Update.html page. Is there something I should
do in ProcessUpdateMessage to indicate the data is wrong and cancel the
update? Or should I put validation before it even gets there?