Hi Todd,
We are trying to reproduce this but can't.
Your web developer should see this "broken page" icon in their address bar:
http://d.pr/i/6jBQ
Clicking on the page icon so that it's no longer broken and is no longer blue turns off compatibility mode. Can he verify that he can NOT do this? Would it be possible for him to get a screenshot showing the inability to toggle between compatibility mode on/off and the broken navigation?
Cheers!