From http://msdn.microsoft.com/en-us/library/jj676915(v=vs.85).aspx:

The X-UA-Compatible header isn't case sensitive; however, it must appear in the header of the webpage (the HEAD section) before all other elements except for the title element and other meta elements.

Currently it appears after, for example, <link rel="shortcut icon"> element.

Solution

In file at_core/inc/alter.inc change line 28 from '#weight' => 1, to '#weight' => -999,

Comments

This must be a regression, I was sure I did this ages ago after lengthy discussions with another user. Hmmm...

Note that this is acutally changing in the dev version, soon, rather than hardcoding for Edge support we will have a field, so you can add any document mode.

Status:Active» Fixed

I've pushed the fixes up to dev.

Status:Fixed» Closed (fixed)

Automatically closed -- issue fixed for 2 weeks with no activity.