My comment was based on an entirely coincidental experimental patch I've been trying for the last week. Following your 'unitless line height' patch I thought I'd try something similar by applying a simple Patch to change
Code:
padding-bottom: %1em !important;
to
Code:
padding-bottom: 0 !important;
to see if the end-of-chapter bug could be improved.
It's quite difficult to be absolutely sure, especially because my own standard styling includes a small non-zero margin-top (0.25em) on standard paragraphs, so I don't expect to see the same number of lines on every page. My gut-feel is that sometimes it has helped to get the last line of some chapters fitted onto the bottom of a page rather than starting a new page for the last few words. Of course, some chapters
do still end on the first line of a new page but again, my gut-feel is that they wouldn't have fitted on the previous page with the existing font-size/line-spacing settings.
I am sure that my testing could have been more scientific but I'm inclined to stick to reading books with my preferred styling for now and just 'suck it and see' for a while
It's been a harmless patch so far, but as I never use padding settings in my standard css it's hard to say whether others who do use it would see some unwanted side-effect.