DOM 0 with XHTML caveat
I'm okay with this, but I love me some backwards-compatible DOM 0, especially when I know exactly which element I need to access via script. Luckily, it's perfectly okay to serve XHTML 1.0 as "HTML compatible" text/html. It's when you start serving XHTML 1.1 as text/html that people start yelling and pointing.
Here's the Bugzilla discussion of this behavior.