Internet Explorer has a mode called "Compatibility Mode", where it changes how rendering and JS execution are performed. This can impact visual styles, page performance, and page functionality. Some customers are required to develop sites for specific capability modes.
This feature is implemented by Internet Explorer by having users manually add sites to the Compatibility Mode settings. This only works when done manually; Currently, neither Selenium nor Sauce Labs have a solution for this. This prevents users from testing pages which rely on Compatibility Mode with Sauce Labs.
Provide a Desired Capability, compatibilityMode, which works for IE based tests. Allow it to take an array of base URLs, which should be added to the Compatibility Mode setting.
The current workaround for this problem is to use a Prerun executable to add sites to this list. For older versions of IE, it was possible to add these directly via a registry key. For IE11, it's still possible, however there's some sort of encoding needed on the URL values.
This workaround is tedious and time consuming, but it could form the basis of a solution. If Sauce Labs can figure out the encoding (which may be easy; I was not sure how to investigate) it wouldn't be difficult to set during test setup, using a similar script to this prerun executable.