Maybe, the angular momentum can be understood as a distortion in the adjacent space-time around the black hole, not the black hole itself. That is: the angular momentum is a property of the adjacent space-time around a black hole. But I have no idea, actually :D
The angular momentum is related to the rotation. And when a black hole has angular momentum, it is said that it is a "rotating black hole". But what does it mean? A black hole does not have a conventional surface, like a basketball. How should we interpret that angular momentum?
I asked this...