From a technical standpoint, this bit:

Even if the alien jeers at you, saying, “The computer said you’d take both boxes, so I left Box B empty! Nyah nyah!” and then opens Box B and shows you that it’s empty, you should still only take Box B and get bupkis. ... The rationale for this eludes easy summary, but the simplest argument is that you might be in the computer’s simulation. In order to make its prediction, the computer would have to simulate the universe itself.

Seems wrong. Omega wouldn't necessarily have to simulate the universe, although that's one option. If it did simulate the universe, showing sim-you an empty box B doesn't tell it much about whether real-you will take box B when you haven't seen that it's empty.

(Not an expert, and I haven't read Good and Real which this is supposedly from, but I do expect to understand this better than a Slate columnist.)

And I think the final two paragraphs go beyond "pokes fun at lesswrong".