I shouldn't have used the word 'irreversible', what I really meant was that it can flow one way but not the other.

*****As this happens over and over again, the particles that escape will be perceived by a distant observer as radiation from the black hole.*****To me, this still seems like you could make any massive object disappear, simply by looking at it. Not really. When you look at an object, you see the light that's reflected off it. The objects acts as a passive reflector. Black hole radiation is a net outflow of energy from the event horizon which causes the black hole to eventually disappear. "Can't you just move a surface relative to an object, and say the object is being irretrievably sucked across it?" You can do that, but if you don't do it, then nothing will happen and the two object will remain apart. In the case of a black hole, the world lines of objects close to an event horizon do not point perpendicularly to the event horizon (as they would when it comes to any other object), but they actually point directly towards it and terminate on it. So, all object close to an even horizon are destined to fall into it. You don't have to move the horizon towards them for that to happen. The effect is intrinsic to the 'distorted' nature of spacetime in the vicinity of a black hole. That is why it is different from anything that you say. "Isn't it the presence of an object that causes spacetime in the first place? Is there any way to detect or interact with space that doesn't lead anywhere? Isn't all space defined by the extent to which it leads to a massive object? Meaning, is there any undistorted space!?" Strictly speaking, one cannot answer the question as there has never been a spacetime without objects in it. But roughly speaking, if one thinks of a region of space (the universe) that has no massive objects in it, then one can safely say that it will be flat and non-distorted. "Define escape. How can I analyze an object empirically, and determine whether or not is has "escaped." Or is this simply saying that everything that eventually falls into a black hole was doomed to fall into the black hole?" Escape means to actually be able to get far away from the black hole and be detected by a very far away observer. A massive object that is sufficiently far away from a black hole, can feel it's gravtitational effect, but if it has enough momentum, it can still avoid falling into it. Of course, as you get closer and closer to a black hole, it gets harder and harder to avoid falling into it. "But how do I draw a line between terrible inconvenience and impossibility?" It's the difference between something that can take place, at least in principle, and something that cannot take place because the laws of nature as we know them forbid it. The laws of nature do not forbid that someone should be able to dive into the pond and get the gold ball back. It's just hard work. The laws of physics forbid a massive object that has fallen into a black hole to reverse its path and get out again. Incidentally, the reason is that that object is following its worldline which tells it how to travel in time. To reverse its direction would be equivalent to travelling back in time, which is forbidden by the laws of physics as we know them.