I'm going to have to distance myself from Alicorn on this one. (Surprise, I know.) I think she's confusing the general meaning of "placebo effect" (any positive effect manifesting in a control case) with the specific meaning (curing of a condition attributable at least in part to believing a treatment to work).
The general meaning of it clearly exists and is mentality-independent. For example, after an oil spill, if you dump oil-eating bugs on one part of the affected area, and not the other (the latter being the control), oil will dissipate even in the control, just by natural processes and not because of the bugs. That's a placebo effect baseline against which to compare the bugs.
I endorse the stronger claim that the specific kind exists, and withstands conscious non-belief, so long as you use other modes to trick your body/brain into believing it. This shouldn't be surprising: you behavior is often hard to consciously modify. For example, it's easier to look confident by having a social group you belong to than by trying to control all the micromovements of muscles necessary to give off confident signals.
If that's what Alicorn meant, I apologize, she didn't err, and I agree with her.
Anticipation and faith are both aspects of the human decision process, in a sense just subroutines of a larger program, but they also generate subjective experiences (qualia) that we value for their own sake. Suppose you ask a religious friend why he doesn’t give up religion, he might say something like “Having faith in God comforts me and I think it is a central part of the human experience. Intellectually I know it’s irrational, but I want to keep my faith anyway. My friends and the government will protect me from making any truly serious mistakes as a result of having too much faith (like falling into dangerous cults or refusing to give medical treatment to my children)."
Personally I've never been religious, so this is just a guess of what someone might say. But these are the kinds of thoughts I have when faced with the prospect of giving up the anticipation of future experiences (after being prompted by Dan Armak). We don't know for sure yet that anticipation is irrational, but it's hard to see how it can be patched up to work in an environment where mind copying and merging are possible, and in the mean time, we have a decision theory (UDT) that seems to work fine, but does not involve any notion of anticipation.
What would you do if true rationality requires giving up something even more fundamental to the human experience than faith? I wonder if anyone is actually willing to take this step, or is this the limit of human rationality, the end of a short journey across the space of possible minds?