Moderators generally copy the other moderators of a particular forum (or, in the case of the senior moderators, each other) such that their actions are known to one another and that if one moderator takes an action that the rest are aware.
It avoids "forum shopping," if you will. There have been members (respected ones, who shall of course remain nameless) who have in the past taken it upon themselves to try to get one moderator to take an action in particular forum or forums after another moderator refused to do so. Or deliberately asked a loaded question to moderators of a particular forum one at a time in the hopes of catching an inconsistant answer. And so forth.
I'm personally of the opinion that any member who might attempt to play one moderator off against another, well, let's say "lacks complete tact and social skills," but that could not have possibly been the case in this instance.
But that's okay--that's why mods tend to cc other mods on PMs.
I agree that it would be nice if it was codified into the software, if for no other reason that the general FT public would not have yet another chance to enjoy the soothing tones of a disgruntled member not getting their way bashing a moderator for no good reason, but I digress.