he is using the %c somehow, I suspect as part of a challenge in a channel game.
using $() in the match text area will allow the code to be smaller as you have it
on *:text:!kill *:#: .describe $chan $2 has been killed
on *:text:$(%c $+ !kill *):#: .describe $chan $$2 has been killed
the second line allows the %c to be part of the matchtext without the if statement
I would guess the channel should be specified but that might not matter
the $$2 prevents it from fireing if someone typed the %c!kill without the nick to kill
