Description of problem:
IE11 declares itself (via its "user-agent" property) as something that resembles Firefox.
This causes the Gecko (Firefox) targeted GWT permutation of the GUI application (web-admin / user-portal) to be loaded into IE11, which my result in unexpected behavioral regressions in the GUI.
By instructing IE11 to emulate IE10, IE11 will declare itself as IE again, which will cause it to load the "ie9" GWT permutation of the application (rather than the "Gecko" one), which (as we already know) is working well on IE10 and similarly, should work well on IE11 while it emulates IE10.
This bug is tracking the code-change that introduces the instruction for IE11 to emulate IE10.