IE doesn't participate in the WPF rendering system, so it would have all kinds of glitches like it sitting above all other controls (referred to in the docs as

IE doesn't participate in the WPF rendering system, so it would have all kinds of glitches like it sitting above all other controls (referred to in the docs as "Airspace Issues"), as well as unthemed controls (specifically the scroll bar - stuck out like a sore thumb). The markup that READMEs use is really simple, IE would've been fine for it.