Processing instructions in Polygot HTML5

The current draft says [1]

  "Processing Instructions . . . are . . . forbidden in polyglot markup"

The xml-stylesheet processing instruction has value, and a uniform
interpretation wrt both XML and HTML processing in HTML5 -- why is it
forbidden in polyglot?

ht

[1] http://dev.w3.org/html5/html-xhtml-author-guide/#PI-and-xml
-- 
       Henry S. Thompson, School of Informatics, University of Edinburgh
      10 Crichton Street, Edinburgh EH8 9AB, SCOTLAND -- (44) 131 650-4440
                Fax: (44) 131 651-1426, e-mail: ht@inf.ed.ac.uk
                       URL: http://www.ltg.ed.ac.uk/~ht/
 [mail from me _always_ has a .sig like this -- mail without it is forged spam]

Received on Wednesday, 30 November 2011 11:58:12 UTC