I just noticed a rendering issue with the Ribbon/Ribbon Window when running with the display scaled above 100%. A thin "border" renders between the ribbon and the ribbon window's title bar. You can see this using the Sample Browser's Document Editor sample and RibbonWindow quick start. The applications render properly when the system's display scaling is set to 100% but at 125% the "border" is visible. I've verified this on Windows 7 and two different Win10 machines. Office 2016 apps do not exhibit this behavior.