The widows and orphan set to "1" (off in other words) is my personal preference when reading. Encountering an unusually large margin at the bottom of a particular "page" (when w&o is set higher) invariably tricks me into thinking I'm encountering the end of a chapter or a scene-break. It doesn't trip me up too badly when a new chapter doesn't follow, but I do tend to stumble a bit while I determine if there was/wasn't a scene-break.
That's also the reason why I deem vertical-spacing
alone to be insufficient for the demarcation of scene breaks in an ebook. If there's no graphic flourish, or any of the other "traditional" indicators, I prefer to see some sort of font-style or -variant (or raised cap) change to the text (after the break). Something that my eye can't possibly overlook. If all content creators did smething like that, I'd personally leave the w&o settings alone for my reading. But since that's unlikely to happen...
