[eschwartz]

Now find an E-Ink ereader that supports EPUB3.

Bringing EPUB3 as a proof is a bad move. It is vastly undersupported.

calibre does not support EPUB3. This is by design, since it is not worth supporting useless formats.

Expecting calibre to generate EPUB3-specific features during standard conversions is just asking for MASSIVE trouble in the vast, vast majority of EPUBs and ereaders.


Note that the Editor will throw a warning/error, but will allow you to use whatever you want (it will in fact never do anything of its own volition, only when told). I do not hold out tremendous hope that any automated tools will provide explicit support for EPUB3 anytime soon.