Yes. I understand empty tags for an anchor or perhaps an index entry. I just don't understand it with regard to a link designed to take you to--or pop up--a foot|end-note reference. Of
course that needs some sort of character(s) between the <a> tags. They always have. You can't go anywhere or pop anything up without link text. There'd be nothing to "click" on in the text.
It seems to me that it would be hard to NOT make inline pop-up references work (on the Kindles that support them) as long as you use the (relatively) standard way footnote links are always constructed.