Thinking on, footnotes on my Sony PRS-T1 required tapping the little numeral which would take me to a separate page, and then tapping a link to get back... if there was one.

Now I've got a Kobo and I'm using kepubs (via the Calibre extended driver) I'm getting the popup windows which are lovely.

I'd just accepted that it was different (better!) but I'd assumed it was just the books I was reading, since the Aura is new enough that I haven't read any of the same books on both yet.