http://tech.lds.org/forum/showthread.php?t=4092
Go to the above topic and through the Edit or Quote you can see where I used the Indent feature near the end of the message.
I also went to Advance Search and typed the keyword "indent" in the box, and came up with several pages of other posts who also have the indent code authored, but are not working.
If you know the cause, then okay. If you do not know the cause, I am available to inquire of the VBulletin Priority Support site to ask (or you may also).
Again, on the Message Box toolbar the feature looks like this:

Thanks,
Michael