Ability Capsule allows you to switch between your Pokémon's abilities, right? I've managed to get a hold of this item while I was in Battle Masion, but never really used it. Some people may find this item to be useful in-game, but when it comes to competitive battling, though, all of its usefulness go away in an instant. When you're battling competitively, items matter. You always have to make sure that you're giving your Pokémon the correct item, and not the wrong one. If you make them hold such a thing like this, then it may limit their performance. If Ability Capsule had an additional effect, though, such as giving some sort of a boost to your overall stats, then maybe it would've been a good item for competitive play. But since it doesn't have it, the item's a bit redundant, in my opinion. d: