For your reading pleasure:
www.elitefourum.com/t/debunking-no-rarity-japanese-base/16536/1
www.elitefourum.com/t/a-guide-explaining-why-no-rarity-comes-from-packs-and-decks/16617/1
www.elitefourum.com/t/could-no-rarity-cards-just-be-misprints/18690/1