Mark-up is something that ordinary users will never understand. "Good enough" is what they want. Printing it to check that it came out right is just fine with t

Mark-up is something that ordinary users will never understand. "Good enough" is what they want. Printing it to check that it came out right is just fine with them. It is simply not worth it for the software to try to make everything perfect. Case in point: my book was edited in Vellum, and it can generate PDF and EPUB. The PDF had a widow (one line at the top of the last page of the chapter), and Vellum just omitted that one-line page. To the reader it seemed like a typo (which it was, in a sense). I "fixed" it by removing a few words up above it, so everything fit on the last full page. But it was only that I knew about widow/orphan control that I could figure that out. Just imagine how much trouble it would be to make things perfectly WYSIWYG on every printer and every type of document.