They have an event horizon. Everything past that is inside the black hole. Things absolutely can and do pass the event horizon. That is how the mass of the black hole increases. That is also the problem the article is addressing. This creates a paradox in that it allows a single quantum particle to be poly-entangled - something that is not allowed by our current understanding of quantum mechanics.
Therefore, what really happens? No one knows for sure. If the no-drama principle correct (which is implied by Einstein's theory of gravity), in that you cannot feel gravity when you are in free-fall, you pass through the event horizon just fine, and then die when you are torn apart by tidal forces. (Of course, the tidal forces kick in outside the event horizon in smaller black holes - but that's beside the point). If the no-drama principle is correct, then there is a fundamental and insoluble contradiction in our understanding of physics. That's the point of the article.
No, stuff that falls inside the black hole stacks up around the event horizon, which really grinds stuff up to the planck scale and transforms it to maximum entropy hawking radiation.
falling into it, it has enough degrees of freedom to put you into any kind of virtual reality, so you might experience falling into a singularity or somehow travelling into an "asymptotically flat spacetime" but I'm certain that the classical picture of a black hole is completely wrong.
stuff that falls inside the black hole stacks up around the event horizon, which really grinds stuff up to the planck scale and transforms it to maximum entropy hawking radiation
This looks like a mixture of misunderstanding the classical picture of a black hole, and misunderstanding how the classical picture is altered by quantum effects.
Classically, stuff that falls inside the black hole does not "stack up" around the horizon; it just falls in, past the horizon and on to the singularity, where it is destroyed.
There is no established theory of how quantum effects alter the classical picture, but there is at least one "semi-classical" picture of how Hawking radiation is produced (the one that Hawking originally came up with) that doesn't require any "grinding up" of infalling matter at the horizon.
And you are welcome to be as certain as you wish. But I would point out that without black holes having an interior, there can be no Hawking radiation in the first place. Your statement is therefore internally inconsistent.
there might be something "on the other side" but there's no reason to believe that it has a 3+1 signature or is anything like the space we know at all.
there might be something "on the other side" but there's no reason to believe that it has a 3+1 signature or is anything like the space we know at all.
There is plenty of reason to believe that, if a horizon does form, the region of spacetime on the other side will be spacetime, not something completely different.
There are some (speculative) reasons to believe that quantum effects might possibly prevent horizons from ever forming, but that would mean there is no "other side".
Particles can't be poly-entangled? Why not? A wavefunction is by definition a function of all particles. Breaking it into a separate function for each particle is merely an approximation to facilitate calculations.
Pardon my lack of precision. I should have said "thoroughly entangled". What you say is true of partial entanglement. But partial entanglement is not what we are dealing with in event-horizons and virtual pairs. As the article states, in order to maintain consistency between observers, all particles must be thoroughly entangled.
Therefore, what really happens? No one knows for sure. If the no-drama principle correct (which is implied by Einstein's theory of gravity), in that you cannot feel gravity when you are in free-fall, you pass through the event horizon just fine, and then die when you are torn apart by tidal forces. (Of course, the tidal forces kick in outside the event horizon in smaller black holes - but that's beside the point). If the no-drama principle is correct, then there is a fundamental and insoluble contradiction in our understanding of physics. That's the point of the article.