I'm not to familiar with CR, but it does look like a problem with CR to me. The problem seems to be +y, although unimplemented, accepts a parameter. So when he does /mode #chan +yu BLAH blah, CR says 'ok BLAH goes with +y, blah goes with +u', however +y doesn't say (as per CHANMODES=) "I take a parameter" so mIRC doesn't know that. Therefore when it gets a +yu BLAH blah, it says "+y no param, +u has param BLAH, and then there is an extra param of blah so just ignore that". Therefore mIRC gets confused with the case. If you just did /mode #chan +u BLAH I assume it doesn't change the case? Therefore it would certainly seem that the problem lies in the fact that +y is not correctly listed in CHANMODES=.