We should probably make sure it works anyway...
So here's the formal feature request.
Users are able to flag a question as a duplicate of a question on the facebook sub-domain:
However, when trying to use the Facebook sub-domain URL in the dialog for closing as exact duplicate, Stack Overflow doesn't recognize the URL:
That question looks like it exists on Stack Overflow to me.
Please fix this to allow links from the Facebook sub-domain to be accepted by the close dialog.
Currently, I have to go an manually edit the URL to take out the