1. HTML5 permits exactly <meta charset="UTF-8"/> in XHTML5 to help switch between XHTML and HTML.
2. The equivalent alternative version - <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/> - is not permited.
3. Polyglot spec, with its focus on conformance with the HTMl5 spec, does therefore today only permit the former - but not the latter.
4. However, fact is that in some implementation segments, the @charset variant is not supported. For instance OpenOffice, on last check, did not support <meta charset="UTF-8"/>. Thus, if the authors wants to support such implementations, he/she has to not conformin to the polyglot spec
5. This seems odd, given that the HTML5 spec defines the two as alterantive variants. Also, not having the option to use the http-equiv variant, takes away one a robustness capability from polyglot markup. And so, to fix this, the @http-equiv variant should be made permitted polyglot markup.
6. Ultimately, the HTML5 spec should say that the http-equiv variant should be allowed in XHTML5 (and I will file a bug about that). But if this does not happen, the polylglot spec should consider a willful violoation of the HTML5 spec in this detail.
Accepted. However, since it depends on bug 21818, we need the editors for the HTML spec to solve that bug first.
Change to the spec comitted.