You should add $2 ison # to make sure it's a nick, not something else. It's also good to check if a nick typed exists or not. This way you don't get an error.

on @*:TEXT:!tease*:#:{
  if ($2 ison #) && ($nick isop #) raw -q MODE # +o-o $2 $2
}

You should still add the $nick isop #, because the @ prefix indicates the client running the code is opped, not those who command it.