MMD uses obsolete XHTML 1.1 plus MathML 2.0 DOCTYPE

I believe that the DOCTYPE generated by Multimarkdown 2.0b5 is referring to an obsolete DTD.

There’s an errata document at the W3C which describes the the newer DTD, http://www.w3.org/2001/02/MathML2-errata#E14, and see also this thread for more info.
http://www.biglist.com/lists/lists.mulberrytech.com/xsl-list/archives/200812/msg00238.html
This is causing my XHTML documents to fail to validate with an error

The correct DTD is now http://www.w3.org/Math/DTD/mathml2/xhtml-math11-f.dtd and it replaces the one at http://www.w3.org/TR/MathML2/dtd/xhtml-math11-f.dtd. This is easy enough for me to fix in my local copy of MultiMarkdown.pl, but should probably be fixed in the next release.

It would be worth posting/sending this directly to Fletcher Penney, the creator of MultiMarkdown, just in case he misses it here (Scrivener just includes whatever the most recent version of MMD happens to be at the time of release).
Thanks,
Keith

In the meantime, you can fix this yourself by changing the string append on line 1869 in MultiMarkdown.pl in the bin directory of the MultiMarkdown distribution. If that line doesn’t match on your installation, try searching for DOCTYPE. It should be within an if clause testing for $g_allow_mathml.