He was clear that the pain in surgery conveys no new information.

Let me try to explain this better, then. Imagine we take a person who needs surgery but was never told by their doctor what part of their body the surgery will be on. We perform the surgery without any anaesthetic and with the patient blindfolded. In this case, the pain is giving new information ("AAAIE! MY RIGHT LEG!") but we still don't approve.

kpreid could clarify that this information is useless (in that the patient doesn't gain anything from knowing) and that (s)he meant useful information. But this isn't true either. I could state before the surgery that I will give the patient ten cents if they can tell me which of their limbs I operated on, but this still wouldn't make it okay to perform surgery without anaesthetic.

The way I would have put kpreid's point is that the pain must provide sufficiently useful information to offset its painfulness. If putting someone under surgery without anaesthetic earned someone ten cents, I would consider it an atrocity, but if it was necessary so that the patient could help guide the surgeon by telling them what they feel, saving the patient's life, then it might be a necessary measure.

However, this seems like straightforward utilitarianism, in which the benefit of getting information must outweigh the cost of having such terrible pain. This means it can't be used as a definition of why pain is a cost.

I would say that pain is a cost for other reasons, but that when pain conveys information, the information can be a counterbalancing factor. This makes it a mistake to say that the reason pain is a cost is that it doesn't convey information, equivalent to saying that the reason bombing civilians in Afghanistan is bad is that it doesn't kill Osama bin Laden. The reason bombing civilians is bad is because murder is wrong. Killing Osama bin Laden would be a potential counterbalancing factor that might justify bombing the civilians, but lack of Osama-killing is not the definition of the evil of murder.

In this context, it's not really possible for someone not to have goals. They might not explicitly be able to state long-term goals, but as long as they're taking deliberate actions, they have goals. And yes, for sufficiently bad goals, you do care how hard it is for the person to carry them out!

Consider someone whose only ambition is to collect every Pokemon in the world. Kpreid's scenario suggests a dichotomy: either it is okay to cause this person pain, or the only reason not to cause this person pain is because it might prevent Pokemons from being collected. I don't think this captures the reason we don't break the bones of Pokemon collectors (even though we all feel sorely tempted sometimes.)