The forums are often full of topics that are directed at the moderators. These messages most often do not need to be public. So, I suggest giving players the ability to send a PM to all moderators at once (similar to the in-game reporting system, but PMs allow for larger and more clear messages as well as images and such). That way, when someone wants to report something to all of the moderators, and it is more convenient to do so through PM than in-game chat, he can avoid posting it in the public forums. Of course, this system would have to strictly moderated to avoid abuse and spam (perhaps rank requirement?).
Note that this would also be much more useful than simply PMing a single mod, because mods are not always available or responsive. So being able to message all of them at once will speed up responses.
I would suggest making this clearly visible in the homepage menus. Perhaps a button saying "Contact Moderators" in either of these locations: