I just tried to report a post here on Area51, about being a support request that should be placed on phpBB.com/community
After I posted the report form, I got this error:
To make sure I went back to the report form and selected another report reason, but with the same result.General Error
SQL ERROR [ mysqli ]
Duplicate entry '0' for key 'PRIMARY' 
An SQL error occurred while fetching this page.
Now I'm not really sure about the version this forum runs on, but reporting goes well on my local 3.2 installation so I guess posting this bug to the issue tracker with the 3.2 label is wrong. Perhaps it's only on this specific installation or branch. I'll happily report this elsewhere if someone points me in the right direction.
For testing purposes, I just tried to report this very post. It resulted in the same error.