That doesn’t answer my question
But anyway -- of course the code is harder to read, but that's not the point, epubs are meant to be read as ebooks, not opened and judged for code legibility. If an ebook was already styled to your preference or you managed to style it externally from an ereader with extensive options (like KOReader) -- meaning you had no reason to open the epub code, you wouldn’t be able to tell the difference between a version with ids and one without. And that's what most people do -- they read the book and they don't notice the extraneous classes, or ids, or comments. Because those things don't do anything.