Just taking an educated guess, but I suspect by "firmware" Kano is referring to the version of cgminer your hardware is using.  e.g.  The manufacturer modified cgminer somehow.  

From Kano's response, it sounds like modified cgminer software has been known to cause problems to pools in the past (block stealing, bad stats, etc.).

Thus he isn't banning you as a personal thing, but rather not allowing your hardware on the pool to protect the pool and its other users.   This feels similar to me to the ban of rental equipment he has in place (Nicehash specifically, plus some others)