vBulletin3.x uses a call upon your setup of your chosen postbit to display the PM in your box. So lets say I use Legacy as I do with a very graphic postbit, the PM system displays that chosen postbit inside your pm message. So to slim out the PM you need to have the above code and use something simple, such as their bland default.
This is based, I think how inside private.php something looks for the postbit determined from your setting in the admincp.
If you change your postbit on your board from legacy and then look at a message , then choose non legacy and look at a message you will notice that the style of your PM has changed. I believe that since I am using legacy as my main setting and the <if> for private (as listed above in that code) has a the code from the postbit (non legacy). That the vBulletin code is over powering you hack and they're must be a way to make something force it to use the non legacy and not leave it up to the chosen selection in the styles portion of options.
That is the best way I can explain it.
see this for info and there is stuff on it as well here
http://www.vbulletin.com/forum/showt...stbit+personal
Thanks