Some books use them as page numbers e.g. <a id="p123"></a> which is handy for a functioning index... and it shuts down the pop-up, if you want to style it that way.
Seems the pop-up breaks the text at every looped <a> only... Just having a link won't do it.
I'm trying to figure out if you can use an empty link & loop to slip subheadings into the footnotes, but KP keeps crashing
Oh and, & or & breaks the pop-up text... get an error message in the pop-up box.