oh, now got the point, then it could be like this:

alias -l issub { if ($1- === $lower($remove($1-,$chr(40),$chr(41),$chr(96))) { return 1 } }

You can get symbols $chr by using //echo -a $asc(`) for example and then seperate the characters to remove from nick, so making the nickname not equal to previous one - not voicing the nick.