And mIRC changes the nick TIEKS to appear as Tieks in the nicklist? That's kind of interesting.
I'd say it's more of mIRC's fault then in this case. I can't imagine why it would be updating the nicklist based off a MODE parameter. I thought it was changing the MODE target nick (<- :
Matt!Matter@irc.mediadriven.ops) to lowercase.
This could be a fun exploit though. People come in with their nick ALLCAPS and an op can lower it for them.
"+y -- Allows a channel op to modify the CaSe of a user's nick as it appears in the channel. (mIRC Only)."