XF 1.5 6000+ threads where starter user id is 0

[dethfire]

Any ideas on what might cause a userid to go to 0? I got 6000+ threads where the thread starter has a name but the id is 0 and there is no profile link. At first I thought maybe it was an import problem from vb but we imported in 2014 and I got this issue as recent as nov 2015.

Here is an example
https://www.physicsforums.com/threads/bolted-assembly-friction-force-clamping-force.843285/

 

[Paul B]

That's a deleted account.

The user name remains but it is no longer linked to a profile/account.