drhowarddrfine - 7:23 pm on Feb 3, 2013 (gmt 0)
In other words, if your page is intended for public consumption, don't use XHTML.
He doesn't say don't use XHTML for public consumption. His wording could be better there but, later, he does say this:
Which is the case since IE9 finally works with XHTML.
Authors who are not willing to use one of the XML MIME types should
stick to writing valid HTML 4.01 for the time being. Once user agents
that support XML and XHTML sent as one of the XML MIME types are
widespread, then authors may reconsider learning and using XHTML.
I don't see where he says that at all though I just scanned it quickly having read it years ago but the Executive Summary says this:
If you DO use XHTML, you should be serving it as such (which will be problematic for public consumption).
If you use XHTML, you should deliver it with the application/xhtml+xml
MIME type. If you do not do so, you should use HTML4 instead of XHTML.
So, again, there is no issue using XHTML and it's included in (X)HTML5. The only problem is search engines as I mentioned above.