It's "gaming the system" for how the inline/pop-up footnotes work on the PW2, so you can slip in headings in the footnotes.xhtml without messing up the contents of the pop-up box. You don't have to do it of course, but the way the Kindle seems to get the info for the pop is from <a> to <a> with links that complete a loop.
The regular loop - with visible links of say, [1] to ^ and back - of course works the way we want: pop-up in PW2 and (probably) just a regular link in Keyboard or iBooks or something.
Empty links can be used to hide text in the pop-up, without having nasty underlines - completing a loop, so the pop-up hides the text, but the links are invisible to the person reading.
If you want to do the following in a footnotes.xhtml:
Code:
Chapter 1 A dark and Stormy Night
1. ^ It's always a dark and stormy night.
2. ^ Actually, it's the end.
Chapter 2 Resurrection Joe
1. ^ He was quite smelly.
... then, in the text, when you tap the [2] link in chapter 1, the pop-up will show:
Code:
^ Actually, it's the end.
Chapter 2 Ressurection Joe
1.
Which is annoying. Adding the empty links will fool the system and NOT show the heading text.
Of course, you could add an emptily link in the footnotes so you could do without the ^ but I think you'd break the functionality in a non-PW2 device...
Does that make sense?