I've got a few questions about Appendix C.

Why is section C14 "Referencing Style Elements when serving as XML"
part of Appendix C "HTML Compatibility Guidelines"?

My understanding is that
  <?xml-stylesheet href="#internalStyle" type="text/css"?> 
is an XML processing instruction. Is this right? If so, why does C14
seem to contradict section C1 (which advises against using XML
processing instructions) by requiring processing instructions?

Why does it require a processing instruction for <style> elements, but
not <link> elements with rel="stylesheet"?

-- 
David Dorward                                      http://dorward.me.uk