You actually CAN do it. It was never stated anywhere that you are not allowed. And being allowed to do something has nothing to do with being ABLE to do it.
I logged my rogue into item and monster, realized I screwed up, switched accounts and then logged my prof into monster and pvp. All things considering this could have worked, switching characters during monster, and then doing item with my rogue and pvp with my prof, however after talking to Pandora, this is a big no no.
One entry per account per ToH, that's what I understand the rule to be.