There is no configuration setting to turn this off. There are various ways to manually disable this.
One is that you can edit the template files to remove all PM references.
Another way is to just leave the PM links but modify the templatesMapping.properties file to change the pm.sendform value to use a new template file that says "This function not available". (Note: The default is to share the same form used for making posts so you can't just change the template).
Both of these are sort of "security by obscurity" methods. If you need to ensure this doesn't work and are familiar with
Java coding, you can look at the PrivateMessageAction class and make sure it doesn't work here. The quick way is to make the sendSave method return a "Function not available" page.
[originally posted on jforum.net by monroe]
