Adding new CSS rules as a string to 'cssText' property of a stylesheet object breaks (some) existing styles in IE11.
The broken styles include viewport adaptation via @-ms-viewport, leading to broken ("zoomed-out desktop version") responsive sites in Windows 8 style IE11 with window width less than 1024px.
Some widely used plugins (incorrectly) use this approach and can thus break your responsive site. Currently, I'm aware of only Facebook's JavaScript SDK doing this - in other words, if you use FB's plugins and include their JS SDK, your responsive site won't work in Windows 8 style IE11 as expected.