"without actually using /debug" -- stop. Use /debug, that's what it's for.
/debug takes the -i switch to call a custom alias, you can have this log your actions much more effectively.
A remote event that triggers when an alias fires would be complicated for many reasons.
First and foremost, you could never use that alias inside the event or you'd end up with a weird recursive scenario.
Secondly, not all users make use of /msg, /me, etc.- mIRC allows you so send /raw commands to the server, and its possible many scripts make use of those- mIRC would have to parse every outgoing /raw command to recognize what kind of event it is, which is a waste of resources.
Thirdly, if you really want to handle *user* input you *should* use the ON INPUT event, not check commands.
Lastly, you didn't really explain what it is you're trying to do.. a logger is a very vague description.
