I have added rule 1.6 to the rules under the JOINING section, which states the following:
1.6 – handlers may handle up to TWO characters at any one time, subject to roster space. If we are at capacity and someone is waiting to join, we may request that a handler drops their second character (provided they are happy to do so), so as to accommodate an addition handler.
I wanted to make that clear because I field a lot of questions about it and realised that there was no official stance on it. So now there is!