Any update on this endeavour ?

Can a project member please indicate where in the Webdriver code, Internet Explorer
is launched?

IE is launched from within the native code (C++) component of the IE driver. The actual
code where the browser is launched is in the LaunchBrowserProcess method in BrowserFactory.cpp[1],
at or about line 34.

[1] http://code.google.com/p/selenium/source/browse/trunk/cpp/IEDriver/BrowserFactory.cpp

I just read Microsoft doc again. There are basically two ways to modify a feature control:

* Using CoInternetSetFeatureEnabled function: http://msdn.microsoft.com/en-us/library/ms537184%28v=vs.85%29.aspx#sec_featurecontrols_overview_functions.

* Editing the key registry (can be done manually with the command regedit): http://msdn.microsoft.com/en-us/library/ms537184%28v=vs.85%29.aspx#sec_fck_registry

Unfortunately, it does not seem that FEATURE_BROWSER_EMULATION can be specified using
the first method (I think it only works for boolean):

http://msdn.microsoft.com/en-us/library/ms537168%28v=vs.85%29.aspx
http://msdn.microsoft.com/en-us/library/ms537169%28v=vs.85%29.aspx

so editing the key registry seems the only possible method here. Code can probably
be written to do that without user interaction. However, I think it will apply for
all IE instances.

I've been asked to share my workaround for this issue. The idea is to cast a Webdriver
object to a Selenium 1 object. Then to use keyboard events method of the Selenium 1
object. See the chooseInternetExplorerDocumentMode function here:

https://github.com/mathjax/MathJax-test/blob/master/testRunner/seleniumMathJax.py

Windows registry entry for FEATURE_BROWSER_EMULATION with settings for IE9/IE8 emulation
modes:

http://msdn.microsoft.com/en-us/library/ee330730(v=vs.85).aspx