These are good points but they are a downside to the approach of code generation, not to abstraction itself. If Sass was interpreted by the browser it wouldn't

These are good points but they are a downside to the approach of code generation, not to abstraction itself. If Sass was interpreted by the browser it wouldn't be the case, so while it's true for the world we live in today, it's not a fundamental issue with the approach itself of having the power of abstraction. So while I accept these as criticism of Sass, I do not accept them as downsides of abstraction. BTW, Sass will emit comments to your CSS to help you track down the original source of your styles. Nevertheless, I think I will add them to the list of downsides, because I don't think we'll have wide browser support for "Abstract Style Sheets" any time soon.