My colleagues at Kobo and I put together this feedback after reviewing the document. Much of this is editorial, with the goal of improving the readability and usability of the documents. There is also some functional feedback too.

1. ONIX Metadata / 1. EPUB Accessibility Metadata

• The entire section is in Notes, which is a bit confusing and makes the content difficult to parse. I'd recommend removing the notes and structuring the content as an introduction more properly.

4.3 Conformance / 4.3 Conformance

• This feels incredibly long and convoluted, and I don’t think accepting A, AA, AAA on their own is informative enough to the user, at Kobo we’ve adopted validation rules that throw out levels if there is no attached version, as it’s not informative enough to what they are conformant to.
• For the EPUB metadata, this also requires additional logic to parse and split the value provided in dcterms:conformsTo which while not difficult, requires additional processing that seems unnecessary.

4.5 Navigation / 4.10 Additional Accessibility Information

• The structure of these sections feels disconnected with the recommendations made in the UX Guidelines document, I wonder if they need to be reconciled structurally? It would be good to represent the information in a common order.
• There was similar structural issues in the EPUB Metadata document.

It was also observed that it would be helpful to review the content of the three documents and ensure they align to one another structurally and content-wise. Mentions of metadata properties in the ONIX and EPUB metadata docs are not made in the main document, which adds to the confusion.