gistfile1.txt

from reading the authors-tools site on schema https://authors.ietf.org/en/templates-and-schemas

I believe you can replace your <!DOCTYPE rfc SYSTEM "rfc2629.dtd" >

with this

<?xml-model href="rfc7991bis.rnc"?>
<!DOCTYPE rfc [
  <!ENTITY nbsp    "&#160;">
  <!ENTITY zwsp   "&#8203;">
  <!ENTITY nbhy   "&#8209;">
  <!ENTITY wj     "&#8288;">
]>


yes, more.  but it also seems to not make xml2rfc complain like it does currently. 

So, my experience of this is that when I tried that, it blew up in my face. Maybe the tools have been fixed since then?

I will experiment some more and return with data !

So in doing tests using the workflow the tools accept this change. Also, when I use the original xml with author-tools.ietf.org and ask for a xml2rfc v3 document, it throws errors "error on line 139 at column 33: Entity 'nbsp' not defined"

this is probably me being overly pedantic.