No, the string -- is not permitted to appear within comments in XML. So the fact you have -- show up inside another comment is going to cause failures.
And trying to post that answer also broke the text entry parsing 😉
For further proof, check the W3C specification:
http://www.w3.org/TR/2008/REC-xml-20081126/#sec-comments
The phrase
For compatibility, the string ” — ” (double-hyphen) MUST NOT occur within comments.]
appears in the first paragraph of the section on XML comments.