Fotiman - 6:55 pm on Feb 3, 2013 (gmt 0)

The second post says:

It is suggested that XHTML delivered as text/html is broken and XHTML delivered as text/xml is risky, so authors intending their work for public consumption should stick to HTML 4.01, and authors who wish to use XHTML should deliver their markup as application/xhtml+xml

(emphasis added is mine)
In other words, if your page is intended for public consumption, don't use XHTML. If you DO use XHTML, you should be serving it as such (which will be problematic for public consumption).