Hello,

Yes, I've also seen this only one time a few days ago. [edit]This was definitely before Micha upgraded this forum to version 2.4.17.[/edit]

In my forum, I saw this behavior one times months ago. It was a single posting (the thread opener). I took a look to the database and realised a missing thread id (was set to zero). The posting/thread was not flagged as spam and it was a real-life user!
I wasn't able to reproduce the error.

/Micha