First of all, Ghost-writer, you were the one who made a suggestion using if $me isin $1-
second, that is one way to go at randomizing messages. I was basically basing my suggestion off the author's script as close as possible.
Finally, for your info, you can also use the /play command with the -r switch:
on *:TEXT:$($+(*,$me,*)):#: { .play -r # bla.txt }
The -r switch forces a single line to be chosen randomly from a file and played. One thing about using /play command is that it provides a default of 1000ms delay per trigger, unless changed otherwise.
P.S. My suggestion was pretty decent.