In my honest opinion it is kinda idiotic that when you want to revenge someone and that person is either already in battle or wearing a shield you loose your chance to revenge them.
Obviously you canīt revenge them at that time but you should be able to do so whenever they come out of battle or when their shield is gone.
It is unfair that you have to wait another 24 hours to try and revenge them again, while you did not even have the chance to do so!!
Itīs rubbish and if you ask me this should be changed.