html entities privatemsg token
You may implement this: hook_privatemsg_message_presave_alter in you custom module and change the message's subject as you like.

Here is a code sample:

/**
 * Implements hook_privatemsg_message_presave_alter().
 */
function your_module_privatemsg_message_presave_alter(&amp;$message) {
  // dsm($message); print out the $message contents
  $message-&gt;subject = "$message-&gt;subject"; // use single or double quotes
}


Tip: strip quotes from a string