Perhaps A Valid Objection
Matt Mullenweg (WordPress) writes that "the feed validator is dead to me."
The managers of the RSS feed validator are proponents of the competing ATOM standard. They feel RSS is inferior and poorly defined, and their attitude is probably perceptible in the validator, its messages, and its frequent changes.
In truth, end-users and Web designers probably needn't care about validators at all. In practice, validators reject lots of things that are "wrong but acceptable" -- like keeping up with highway traffic even though everyone is moving at or above the speed limit. Validators also tend to reject some things that are debatable, customs more honored in the breach than the observance.
This is neither religion nor ethics. If the standard says, "do this" and the software people actually use says, "I expect that", would you prefer that your Web page or feed be right, or would you prefer that it work?