deskthority

Hm...since I don't know all that much about electronics:
Does the controller have to know about the diodes in a matrix or can I make keyboard MOARKRO by adding diodes to the switches?

Unfortunately not. If the keyboard wasn't designed to be NKRO then, in most cases, adding diodes won't make it NKRO unless the controller is also reprogrammed. This is because on most 2KRO boards the controller is hard coded to use blocking to prevent ghost keys from being registered when more than two keys are pressed simultaneously. If you can't switch off blocking then you won't get true NKRO even with diodes.