Contributing again;
You can group if events to make the code cleaner. For example:

 if ($isowner($chan,$nick) == $false) { 
  if ($isadmin($chan,$nick) == $true) { etc }
  if ($nick isop $chan && $isadmin($nick,$chan) == $false) { etc }
} 

You could also just use one haltdef at the end. And why do you include echo -m $nick in your channel text event?