Well right now it can be used explicitly to prevent mIRC from showing the key to people who would otherwise be able to see it*. Also it breaks any auto-rejoin actions made by mIRC (rejoin on kick, /hop, etc.), so there's a couple of potential uses for it right there. Regardless of that, the point is there's something happening here that is not desired behaviour, not expected behaviour, and can be fixed with a very simple check. It's a bug that can be fixed - so it should be.
*: Yes I know they'd still be able to see the mode line when the change happens but that relies on them to actually see that line and know what it means. Many people new to IRC no doubt wouldn't know and instead rely on the channel central to provide all the info.
