Hi Bill
An update:
> I believe the answer to the first is "yes". For one thing, I think the LaTeX being submitted to arXiv (arxiv.org) is improving. I commonly look at arXiv source and try to run it through tex4ht toward html+mathml with mathjax. I see success there as a sign of well-structured LaTeX. But I've not made a systematic investigation on this point.
But Bruce and Gabor have. They have worked on the whole arXiv (to produce, in particular, very information-rich MathML) as part of the semantic maths project. So they can probably give you lots of useful data on this and on many other subjects of interest to LATEX-L discussions.
Best,
chris