Hehe I don't think we're in disagreement at all, but your point about unrealircd does change things a little. The problem is that if freenode's ircd and unrealircd both report +q as being a regular channel list mode and not a prefix, then mIRC will have a hard time distinguishing between the two cases. This would be fine, since unrealircd is the one using the notion of ownership in a nonstandard way [*] and there is no matching "on QUIET" for freenode either (etc), except that my suggested fix of using the 005 PREFIX would break "on OWNER" on unrealircd, which is presumably not going to make its users happier either. If this is indeed limited to unrealircd, then doing an ircd name check on unrealircd could preserve the current behavior on those servers, while still fixing the bug in general, but it does make the fix a little bit more complicated.
[*] although historically it might not have been nonstandard at the time it was added to unrealircd, since the owner prefix is apparently an IRCX concept which gradually made it into regular IRC servers? I'm not sure, but either way, the prefix version of ownership seems to be the common one now..