Oh, the irony!

Microsoft’s RSS Team: “Feeds and well-formed XML”

Hence, we’ve adopted the following overriding principle for IE 7 and RSS platform in Windows Vista:
We will only support feeds that are well-formed XML.

Funnily enough, their own Atom feed does not validate, according to feedvalidator.org (the RSS feed does).

I do realize that well-formedness and validation aren’t the same, and both XML files do seem well-formed. But if they have well-formedness as a goal for a very simple reason:

This principle allows us to build a more predictable feed parser.

… , then why not make that feed parser even more predictable by requiring validation as well?