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> - The event horizon is a two-dimensional sphere and, being two-dimensional, has zero mass and cannot exert any gravitational force.

Stop right there. A two dimensional surface can have mass if it has infinite density. And infinite density makes as much sense as any other sort of singularity...

Where's the singularity that occurs if we assume it's just a region of space with nothing in it? I didn't call the black hole a zero-dimensional point.

We don’t know, and may have no way of knowing. There are conjectures that the event horizon is it, that inside the event horizon is a quantum fuzz ball, or strings, or 1D points, or a whole universe. We don’t know, and may well never know. What we do know is that it seems a 2D horizon can encode the information required to describe a 3D volume, and that goes for event horizons, as well certain classes of cosmic horizons in some models. This weirdness is the core of the holographic principle conjecture.

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