Yay, yay, yay! Firmware 3.1.1 was immediately available for over-the-air updating here in Toronto. My Kobo Aura HD, Aura, and Glo all updated flawlessly, and I'm delighted to report that on all three models the problem with vertical spacing being lost between elements in many .kepub.epub books rendered via ACCESS has been solved. I'm delighted.
Hats off to Kobo for taking this seriously and quickly fixing the problem!
Rob