There are many people who create a username not so they can post, but so that the can be informed of new posts each time they log in. It could be that is the case.
go to a profile, any ones will do and in the address bar, change the number thats in there to some random number about the same length, you find loads and loads of users with zero posts, for just the reason DB said.
Blackwave perhaps?
If it ain't broke.....pull it down and see how it works anyway!