Maybe you didn't look hard enough
Because I found:
The rest are echoed by mIRC itself.
I guess you could try changing the notify list part by manipulating watch list raws (602-606 - two of them are the notify and unotify events) but I guess it is server-dependable and still don't know if you can halt the mIRC message.
Try using /debug @anywindowhere
You can see if it is an event (either remote, ctcp or raw) there.
And:
I think you can do it that way, but you might want to look at the ISON raw too:
--------------------------------------------------------------------------------
303 yournick :[watchnick]
--------------------------------------------------------------------------------
If [watchnick] is there, then the nick is online, otherwise offline.
