I think it comes down to how define the black hole.
If you go by the event horizon and say if “it” (anything) cannot escape back to the rest of the universe then it’s part of the black hole you have a definable boundary you can predict based on mass.
On the other hand you could say that all the mass has been reduced to a point singularity and is removed from the universe except for mass, charge and angular momentum.
The most interesting property to me is the conservation of angular momentum. Mathematically there is a limit to how much angular momentum a black hole can have.
So if you selectively fed a black hole mass with positive angular momentum you should be able to get to a point where it cannot consume anymore matter with “positive” A.M. but will accept mass with “negative” A.M.
That is weirdness to ponder. 
Cheers
G