You only have problems if you try to
switch to application/xhtml+xml, which is easy to solve: don't do that
if we were outputting HTML4, it might cause ∗genuine∗ problems - e.g. if you need XHTML in order to mix in MathML or SVG
.. to do which you must serve as application/xhtml+xml.
That said, I agree with his points. And personally I wish the browsers would relax the restrictions on when they will agree to render SVG. I see no good reason why they refuse to do svg in text/html mode, considering the exceptions they make for seemingly everything else.