A11Y orthogonal to the HTML/XHTML Compatibility Authoring Guidelines?

Rich, 

you voted 'Abstain' on the 'HTML/XHTML Compatibility Authoring 
Guidelines'.

You used the justification 'This is orthogonal to what I work on'.

However, this does relate to ARIA. Example: for the grid role, ARIA 
says: [1]

]]
Authors MUST ensure that elements with role gridcell are owned by 
elements with role row, which in turn are owned by an element with role 
rowgroup, grid or treegrid. 
[[

And note, that if a (X)HTML document with a <table>, but without an 
explicit <tbody> element is served as both XHTML and HTML, then the 
XHTML document will not have any rowgroup element - <tbody>, whereas 
the HTML-served document will.

Any A11Y member should think about the same issue. Polyglot Markup also 
relates to A11Y.

[1] http://www.w3.org/TR/wai-aria/complete#grid
-- 
Leif Halvard Silli