After importing a document with the non-static text endnotes option, I applied a superscript character style to the endnote numbers and when I export to ePub 3.0 the superscripting disappears. The numbers references in the text are still superscripted as they should be, but the superscripting on the numbers before each endnote at the end of document has been dropped. For some reason Epub Export overrides the applied character style.