See the thread ”During HTML parsing, are *all* named character references replaced by their corresponding glyph?”, and in particular this answer from Michael: 

http://www.w3.org/mid/20130624113437.GB37583@sideshowbarker

What Michael said, is easy to forget. Thus, I think this subject needs a little more description in Polyglot Markup. Right now, only <script> and <style> are covered - and also <noscript>.

I would propose to

  a) ad a section that describes the general issue of content
     that, unlike in XML, is treated as text by the HTML parser
     Motivation: This a an important and general gotcha and 
     difference, both within pure HTML, but especialy when
     creating polyglots.

  b) In practise, this means listing all the elements
     that themselves - or their children, are treated
     as text by the HTML parsers. (This includes
     all elements that begins with the string “<no”, such
     as <noscript> and <noframe>, as well as <script>,
     <style>, <xmp>, <iframe> and perhaps some more (?)

     NB: It may also make sense to mention, in a note
         that the “sane” elements, such as <object>,
         <video> etc, are not treated that way.

  c) The section should give the various usage rules 
     - some elements are forbidden etc, while others
     have special rules for polyglots under this
     heading. (Thus, the script/style should go there
     - or at least be represented with a link to the
     section where their rules are described.)

Btw, note that HTML5 already says that the content of iframe must be empty in XML, so describing iframe should be a nobrainer. See http://www.w3.org/TR/html5/embedded-content-0.html#iframe-content-model
And HTML5 has similar things to say about most - if not of these elements, so it is mostly a collection job.