I can totally get behind the whole “don’t include libraries/polyfills/etc if you don’t need them” sentiment. But as for wrapping some IE conditionals around html/body/etc in order to give you readymade CSS classes for older browsers, where’s the harm in that?

I’ve come to lean on “.lt-ie9” etc in order to do small IE tweaks like giving specific elements layout (or whatever needs to be done to them) without having to think about IE-specific CSS files and the like. I’ve just worked it into my personal starting point/bag of CSS tools. I can’t imagine that it really introduces so much overhead that it makes sense to strip them from any project that (happily) doesn’t need IE tweaks/fixes?