TLDR: reinforcement learning cannot handle AGI, because reinforcement learning rewards must be finite, but a true artificial intelligence could reason about infinite numbers. I think this is complete nonsense. Humans don't receive infinite rewards, either, but we still think about infinite numbers. We typically think about infinite numbers in terms of finite representations, like finite proofs about their properties.…
Is that an accurate TL;DR? I'm pretty sure no... It's not saying you need rewards that are infinite in value per se. It's saying that you might have more situations that need to be differentiated from each other than there are real numbers. For instance, you might need to have one set of rewards that map to the real numbers, and then another set of rewards that also map to the real numbers when compared to themselves…
The author demonstrates that a system without such a capability would not be able to solve a certain set of problems. However, going from that claim to a claim that this capability is needed for human level AGI is a non-sequitur - there is no evidence that such a capability is needed for human-level intelligence, and there's no evidence (at least not mentioned in the paper) that humans have the exact capability described.