Please make an option so you can choose not to receive mail when someone is added to the CC-list, as this doesn't change anything in the bug.
Good idea. :-] (I guess that I'm one of the offenders who lead to this request :-})
I will look into this when I am in Bugzilla fixing gear in the near future. This at first glance does not look like a trivial change but I am sure there is a way.
Are there any plans to merge the mozilla.org Bugzilla changes back into RedHat's version? That would solve this problem (and a huge number of other ones) since their Bugzilla allows people to choose when they want to receive e-mails.
Go to http://bugzilla.redhat.com/bugzilla/userprefs.cgi?tab=email and uncheck everything in the "CC field changed" line.