The only change I make for ebooks (from the print convention) is instead of a blank line to indicate a new scene, I use a centered "* * * * " because since you don't have control over page formatting the blank line could be the last on a page or the first on the next page in which case the reader wouldn't even see it and not know it's a scene change. I actually go one step further by having blank lines before and after the "* * * *." I really want a scene change to stand out.
Using "* * * *" for a section break only works on websites like SOL, where they substitute those symbols for a horizontal line figure < hl> in html. For books, I typically use either a graphic or underscores "__________", since they make for a more pleasing visual image.
Typically, you can add spaces before and after any paragraph through the paragraph style definition (CSS in ebooks and websites).
However, most ebooks sites (smashwords, lulu, etc.) all specify that you can select either indented text or a blank line to signify new paragraphs, showing there is no consistent requirement about which is used.