You have succeeded to mix together an unbased personal accusation with a difficult epistemic problem. The complexity of the problem makes it difficult to exactly point out the inappropriateness of the offense... but obviously, it is there, readers see it and downvote accordingly.
The epistemic problem is basicly this: feeling good is an important part of everyone's utility function. If a belief X makes one happy, shouldn't it be rational (as in: increasing expected utility) to believe it, even if it's false? Especially if the belief is unfalsifiable, so the happiness caused by belief will never be countered by a sadness of falsification.
And then you pick Luke as an example, accusing him that this is exactly what he is doing (kind of wireheading himself psychologically). Since what Luke is doing is a group value here, you have added a generous dose of mindkilling to a question that is rather difficult even without doing so. But even without that, it's unnecessarily personally offensive.
The correct answer is along the lines that if Luke has also something else in his utility function, believing a false belief may prevent him from getting it. (Because he might wait for Singularity to provide him this thing, which would never happen; but without this belief he might have followed his goal directly and achieved it.) If the expected utility of achieving those other goals is greater than expected utility of feeling good by thinking false thoughts, then false belief is a net loss, and it even prevents one from realizing and fixing it. But this explanation can be countered by more epistemic problems, etc.
For now, let me just state openly that I would prefer to discuss difficult epistemic problems in a thread without this kind of contributions. Maybe even on a website without this kind of contributions.
Someone who claims to have read "the vast majority" of the Sequences recently misinterpreted me to be saying that I "accept 'life success' as an important metric for rationality." This may be a common confusion among LessWrongers due to statements like "rationality is systematized winning" and "be careful… any time you find yourself defining the [rationalist] as someone other than the agent who is currently smiling from on top of a giant heap of utility."
So, let me explain why Actual Winning isn't a strong measure of rationality.
In cognitive science, the "Standard Picture" (Stein 1996) of rationality is that rationality is a normative concept defined by logic, Bayesian probability theory, and Bayesian decision theory (aka "rational choice theory"). (Also see the standard textbooks on judgment and decision-making, e.g. Thinking and Deciding and Rational Choice in an Uncertain World.) Oaksford & Chater (2012) explain:
Is it meaningful to attempt to develop a general theory of rationality at all? We might tentatively suggest that it is a prima facie sign of irrationality to believe in alien abduction, or to will a sports team to win in order to increase their chance of victory. But these views or actions might be entirely rational, given suitably nonstandard background beliefs about other alien activity and the general efficacy of psychic powers. Irrationality may, though, be ascribed if there is a clash between a particular belief or behavior and such background assumptions. Thus, a thorough-going physicalist may, perhaps, be accused of irrationality if she simultaneously believes in psychic powers. A theory of rationality cannot, therefore, be viewed as clarifying either what people should believe or how people should act—but it can determine whether beliefs and behaviors are compatible. Similarly, a theory of rational choice cannot determine whether it is rational to smoke or to exercise daily; but it might clarify whether a particular choice is compatible with other beliefs and choices.
From this viewpoint, normative theories can be viewed as clarifying conditions of consistency… Logic can be viewed as studying the notion of consistency over beliefs. Probability… studies consistency over degrees of belief. Rational choice theory studies the consistency of beliefs and values with choices.
Thus, one could have highly rational beliefs and make highly rational choices and still fail to win due to akrasia, lack of resources, lack of intelligence, and so on. Like intelligence and money, rationality is only a ceteris paribus predictor of success.
So while it's empirically true (Stanovich 2010) that rationality is a predictor of life success, it's a weak one. (At least, it's a weak predictor of success at the levels of human rationality we are capable of training today.) If you want to more reliably achieve life success, I recommend inheriting a billion dollars or, failing that, being born+raised to have an excellent work ethic and low akrasia.
The reason you should "be careful… any time you find yourself defining the [rationalist] as someone other than the agent who is currently smiling from on top of a giant heap of utility" is because you should "never end up envying someone else's mere choices." You are still allowed to envy their resources, intelligence, work ethic, mastery over akrasia, and other predictors of success.