I'm an op in a small channel on a small network where occasionally a chatter will
fall asleep at their keyboard, and sometimes they will manage to lean on a key or
two and channel gets inundated with large blocks of nonsense repeated letters.

It finally dawned on me that I have absolutely no idea why their text is sending
whenever their editbox is 'full'. My mIRC does not behave that way.

Is this a mIRC options setting? Is it a Windows setting? Any ideas?

Granted this is very easy to deal with when it happens; just kick the user.
But if the problem can easily be prevented that would surely be preferable.

Grateful for any clues.