Rogers Cadenhead: One line can cause an incredible amount of trouble, which is why every line in a spec has to be precise, thoroughly vetted, and developed within a framework for resolving disagreements and moving on.
One minor point of clarification, of little consequence.
Take a closer look at that one line. In particular, look at the date on the left and on the right. Now look at the prior revision.
That one line of code was in place for 5 minutes and 45 seconds, and never deployed.
Prior to April 5, the Feed Validator treated the wfw namespace as an unknown extension, and did not validate it further. When I added support for it, I initially got it wrong, investigated, and made a correction. The message is now a warning.
Meanwhile, in another specification entirely, take a look at the namespace declaration. Now take a look at examples 2, 3, 4, 5.
Per the authors, the specification takes precedence over the examples.
Expect a lot more warnings.