OK, now I have (what I think are) full conversions of all the procedure,
syntax and variable definitions in three tricky SRFIs:

*
https://github.com/lassik/srfi-markup-proposal/blob/master/arglist-generator/srfi-1.lisp

*
https://github.com/lassik/srfi-markup-proposal/blob/master/arglist-generator/srfi-51.lisp

*
https://github.com/lassik/srfi-markup-proposal/blob/master/arglist-generator/srfi-81.lisp

Edits I had to make to the HTML:

* class="proc/syntax/variable def"
* Some missing closing tags to appease BeautifulSoup
* Consistent use of angle brackets <...> to mean placeholder variables
   and no-angle-brackets to mean quoted symbols in syntax definitions.
   In procedure definitions it doesn't matter which convention is used.
* Nothing else, I believe.