"Ribbon" is an ability, not an item - that's where FFX is different from other games in the series. Ribbon is a skill, unique to the PAL version, which can be added to armour. It protects against all status abnormalities, even the powerful status attacks by the Dark Aeons which normally can't be blocked by anything, even Stoneproof, Deathproof and so forth.

I've got a few pieces of armour with this ability, but I won them from Dark Aeon fights. Dark Matter is too valuable to waste on adding this one ability.