That's not true, if the first two ascii values are the same, the next two are compared, then the third, etc:
$iif(ab > aa,$true,$false) = $true
I stand corrected.
This must be an extension of the aforementioned feature, as in alphabetical terms, ab is indeed greater than aa. Eg. take a look at your Excel spreadsheets and scroll down. The columns go
A B C D E F G H I J K L M N O PQ R S T U V W X Y Z AA AB AC AD AE etc..
So mIRC's alphabetical comparison system is even more complex than I thought.