Conclusion: Armor will be allowed, however it cannot be made to reduce the force of impact or protect against sharp edges. Instead, it can be used as equipment to perform more passive abilities; like resisting certain elements (via a fire retardant cloth) or preventing toxic fumes from entering the lungs (via a gas mask). You can have armor for aesthetic purposes though, as long as it doesn't actually do anything in matters of defense. Such as having a Samurai Chest plate; that doesn't actually protect you from cut wounds (Don't ask how it's possible, be creative ). In matters of how they'll be regulated; it'll be the same as jutsu, weapons, summons, etc. The moderator will deem what is a fair amount of 'defense' this equipment may offer based on its rank and other factors such as size and realistic use. Basically; the best you'll get is limited defense toward an element.

The reasoning behind this limitation is rather simple: If we allowed armor, it would become increasingly difficult for a battle to resolve itself without one of the two parties exhausting their chakra pools. It's very difficult to land a hit on a Naruto RP as it is; due to all characters being ninja, which are known for being very evasive. However with armor, even a good hit would do very little damage because of its ability to take a absorb that hit for the character. As such, armor would be deemed very detrimental to the RP experience, and aren't really something ninja should be wearing. The canon doesn't have many ninja with suits of armor after all.