For editorial comments or suggestions such as cross references, I added them directly to the document and they'll appear in the next draft.
Some assistive technologies are dependent user agents.
A special keyboard, though an assistive technology, is not a dependent user agent. We will never come up with a water-tight definition of user agent or assistive technology. By defining conformance based on sets of checkpoints, we sidestep the need for a precise definition - we are arbitrarily choosing sets of checkpoints based on common and important relationships between desktop graphical browsers and some assistive technologies. The division in two may not suffice in that some software may not fall neatly into one category or the other. This is a limitation of this solution we've adopted.