I've added a page to the Wiki in an attempt to put all of our previous discussion and what documentation I can find regarding overconstraint, anomalous documents, etc. It's located at:
I'd like to make this part of a general documentation of layout design in general, and hope to be a strong facilitator in its development on the Wiki. I welcome anyone who's had anything to say about overconstraint or other anomalous conditions in the past to start putting their ideas up on the page. With a little work, I think we can start incorporating a design for overconstraint resolution into the HEAD layout managers. I see the rudiments of that system already forming, so I think we've got a good starting point.