One thing nobody realizes is that a user can change his or her nickname to avoid being kicked. Here is my take on yours:

on @*:text:*:#:{
  tokenize 32 $strip($1-)
  if ($nick == %kick) {
    kick # $v1
  }
  if ($nick isop #) && ($regex($1,/^!ko(n|ff)/iS)) {
    if ($regml(1) == n) && ($$2 ison #) {
      set %kick $2
      msg # $2 next time you get talk you will be kicked
      halt
    }
    msg # %kick you have been taken off the kick list
    unset %kick
  }
}

As Savage_CL has pinpointed that this script can only watch one nickname at a time, so you may want to consider using $addtok() / $istok() and $remtok() to match more than one nickname.