There is no "blessed" style for proposals, nor is there any standard for
"conforming" HTML¹; different authors' papers frequently look different.
(¹ Aside from the HTML specification itself, of course.)
Personally, I prefer using reST to write my proposals and HTML for final
output. Outputting HTML allows readers to resize or even restyle the
text and read it at a comfortable width, rather than forcing a
particular layout on them. It's also more conducive to being read inline
when publishing drafts via e-mail, which can be a major point for some
people.
(And I prefer reST over markdown because the latter is more featureful.
It's just about worth it for the `contents` directive alone...)
If you're interested in trying out reST → HTML (requires
python-docutils) for proposal writing, you can check out my proposals at
https://github.com/mwoehlke/cpp-proposals.
--
Matthew