[Quoth]

The Kindle Keyboard B008 at FW 3.4.3 (last version) does seem to to support KF8. The B009 (DXG) has less RAM, so no doubt that's why it never did and has a much older last Firmware.

Isn't Hitch claiming that one issue is WHICH version of the Comic Creating SW was used?
Personally I'd do each frame as an image so that on a big enough display an entire panel/page or at worse a row (on landscape) is visible but that on smaller or lower resolution the screens the image lines would wrap so only one cell across the screen. I'd make it as an epub2 and upload that to KDP.
I think that would work on ALL eink (assume maybe a minimum screen of 800 x 600?) and some would display entire?

I just sent an AZW from Calibre to the Kindle Keyboard. It does work, though you have to manually select Publisher Font, or it looks like a mobi. Definately an AZW file, not a dual mobi. Though not an Amazon AZW. Gutenberg epub edited and converted by Calibre. However, Amazon USA sends that Kindle a plain old mobi version of books, not the fancier KF8 / AZW / Embedded fonts versions.

I had so many weird small issues with docx and then Amazon told me just to upload epub2 to KDP. No issues since. Even claims enhanced Typesetting (KFX downloads).