One philosophy is that if the browser is old enough to not support media queries then they should deal with the stripped down, mobile-first version of the site

One philosophy is that if the browser is old enough to not support media queries then they should deal with the stripped down, mobile-first version of the site that they get anyway. At that point, just create a separate IE8 stylesheet loaded with conditional comments to fix the most annoying issues so that the site is at least functional for that type of visitor. There's no reason to bloat the main stylesheet with useless crap for old versions of IE.