RE: Validity

> Can you please provide a real example of an assistive technology 
> doesn't work as a result of invalid code, where all WAI guidelines pass? 

I do not believe that the above is controversial as examples are numerous.  Am I wrong about that Matt? 

The most intractable problem is with nested tables.  Things get better with each release, but I must have heard Jaws announce “not in a table” (when cursor clearly is in a cell) literally thousands of times.  I am a little burned out by this.  Repairing the html fragment resolves the issue about three-fourths of the time.

We wave our hands and pretend this is a violation of WCAG1 5.1 or 5.2 (actually 508 1194.22 g or h) but we know that is stretching the truth.

I will repeat my often-made but never satisfied plea:  Please name three mainstream site that nominally pay attention to validity -- but not accessibility -- that have non-trivial WCAG1 P1 violations.  Matt (and others) have offered compelling sounding theories why this is so, but no evidence, and nothing that satisfactorily explains the improbably high level of one-way correlation.