Maybe this bug only affects certain people because I get the timer as soon as I've revenged someone and cannot hit them again for 24hrs unless they're out in the wild. And does a shield prevent you from being revenged? I didn't and wouldn't think so as you can also be revenged while you're in Aerie which is a safe spot. Being revenged can happen at any time but I agree someone should only be able to do this once unless they bump into you again in the wild.