I'd like to add another possibility to the mix of ideas we're discussing.  Perhaps this is obvious, and perhaps it has been said by someone else and I missed it, but it seems worth restating even if so: There's no reason that we can't have both light markup and an external file.  If we update srfi-template.html with examples of light HTML markup, then authors are likely to use that markup.  That will at least give us a starting point for providing more detailed information, e.g. in a separate file of s-expressions.  Yes, the two files may get out of sync, but since SRFIs don't change once they've been finalized (except to fix errors), that is unlikely and should be easy to manage.