Kevin sent an email notifying me that my RSS feed wasn’t validating. Thanks to him, I implemented the solution here and now the feed validates.

For those who don’t like editing PHP files, Kathy Kinsley has a number of helpful solutions. (As a bonus, Kathy’s provided help for those of us WordPress users whose fingers are getting worn out hitting ‘Delete This Comment’ thanks to the increasing onslaught of comment spammers.)

Thanks you two!