Is there something wrong with the system that shows what appear to be PM's in the Status Updates section.
Four out of the top five status updates are seemingly PM's and it happens regularly anyway.
Someone is going to post something in there that they would rather not broadcast to everyone sooner or later.
It was a new feature when the site moved to a new server. It was intended as a bit of fun, an add on. It's not been massively used but some seem to like it.