I think you need to reassess your concept of how much space and bandwidth things like empty selectors actually consume. First, unless you have 50+ unused selectors, you'd be unlikely to see more than a 10ms increase in download time. Css is also cached and compressed if configured properly, so the size is significantly less (0 aside from initial load). They are good points from a readability standpoint, but there are much smarter ways to optimizing performance than worrying about a few dozen characters in a css file.
I think you need to reassess your concept of how much space and bandwidth things like empty selectors actually consume. First, unless you have 50+ unused selectors, you'd be unlikely to see more than a 10ms increase in download time. Css is also cached and compressed if configured properly, so the size is significantly less (0 aside from initial load). They are good points from a readability standpoint, but there are much smarter ways to optimizing performance than worrying about a few dozen characters in a css file.
I know it's only a very small fraction. But it also has something to do with clean code and helps to make it easier to read or search the code.
Anyway, thanks for your comment! :)