Originally Posted by dwig
I've found both what I think of as "soft" scene breaks (extra blank space) and "hard" scene breaks (extra space with an ornament, three asterisks, or horizontal rule) in books. Usually a book uses one style or the other, but I've seen the occasional book, both printed and ebook, that use both, one indicating a small jump and the other a larger one.
When massaging ebook files I habitually replace the old text convention (***) with a horizontal rule (25% width is my preference) and make sure that there is a non-breaking space in the "soft" scene breaks if they are done with simple paragraph tags (<p>, I replace any <p></p> pairs with <p> </p>) instead of a CSS style. I haven't encountered it myself, but I've read that some ereader software ignore empty paragraphs and therefore don't display the extra blank space when a simple <p></p> pair is used.
The format scene breaks option under heuristics is doing things along these lines - although scene break detection is currently only working in a couple special cases and really needs a some more work put into it. One of the things that I'm starting to dislike about 'soft' breaks is that they really don't work with ebooks. With a printed book the publisher will always make sure a soft break winds up in the middle of the page so it's obvious to the reader. With reflowable books more often than not a soft break will wind up on a page break, and then the user won't even realize it was supposed to be a softbreak. So the idea of the format scene breaks option just replaces all scene breaks with horizontal rules.