User blog comment:Atanchan/A New Innate for Ashe/@comment-25187669-20140920205229/@comment-25187669-20140921120356

You don't get it "Impairing an enemy's movement several times in quick succession removes movement speed increasing buffs from the target" For that you would have to slow Yi with your Q a few times, but if he uses his ult before that you can't even slow him so you can't impair his movement meaning his ult MS wouldn't be gone