Yeah I see what you mean, seems sorta like a bug. For everyone who doesn't see what he means, type:
/debug
you get:
* Debug output off
type:
/debug @debug
you get:
* Debug output on (@debug)
type:
/window -c @debug
type:
/debug
you get:
* Debug output on (@debug)
type:
/debug off
you get:
* Debug output off
type:
/debug
you get:
* Debug output off

What he is saying is, why is it, after I close @debug, mIRC is still telling me it is logging to @debug and that debugging is still on. You shouldn't have to close the @debug window and /debug off, closing the window should implicitly call /debug off.