just put whatever "word" you want for the command and recompile ur server then it is done...
For Example
mutearea: ["stfu"]
change to
mutearea: ["stfu","mute","shutup"]
then in game you should be able to use @mute / @shutup
correct if i am wrong~
you have to seek help in 3ceam for this..since rAthena havent start develop on this yet..
so asking at 3ceam board would be better for you to solve your problem