If using the correct form of K-ON! is "against policy", then first off the policy should be changed because this site is supposed to provide information, but all you're doing is confusing people. At least note in the article that it's supposed to be K-ON!. If you won't have "K-ON!" as the page name, then it should be "K-on!", because it's not two words, it's a stylization of one word. This is the same reason the band's name is "Ho-kago Tea Time", not "Ho-Kago Tea Time", which you did put correctly here. "K-ON!" would be ideal, "K-on!" would be acceptable, but "K-On!" is just nonsense.