I cannot find the string post.id in any file on my system.
I suspect there is a bad edit expression somewhere that got triggered by post.postid and "corrected" it to post.id.
I have no idea how to go about finding this. Is the a standard regular expression that is used to find duplicate strings sequentially in text? If so, I could probably search for that.
I do not think this is a vBulletin problem since it would have blown up the world for them. It happens on every attempt to move a post on my message board.