There's a lot I want to reply to in your post there, I'll see if I can tie it all together somewhat.
Right, and I can see where Joshs is coming from because I think Landa's thesis is somewhat obscured here because we are starting with Chapter 6. The earlier parts of the book are all on Nietzschean heros. This section is specifically on villain characters who are nonetheless embraced in some sense. The thesis is not that Nietzsche supports villains above heroes, but rather his relationship to a certain sort of response to a certain sort of villain that has evolved in Western culture.
I think, to your point, this insight, a sort of self-knowledge and self-respect vis-á-vis one's own (and the world's) arationality and amorality underscores the admiration for a sort of villain: the "insane" villain who is merely being honest about the greater insanity of their own context, and is thus in a sense performing an act of self-mastery and yes-saying, affirming the world-that-is and not the imagined moral world-that-ought-to-be that is ultimately mere delusion. The Joker is a sort of paradigmatic case here. — Count Timothy von Icarus
The insanity or madness Nietzsche is often talking favorably about in his works is not the insanity of a nihilistic Joker or some of these unhinged villains you see in Western Culture. It is rather a kind of noble man, the man of passion. He calls it madness because passion is juxtaposed to being reasonable, to being concerned with utility (The conscious mind reasoning with language, is using concepts that are common to the group in origin, and therefor often concerned with utility for the group). The passionate man is mad or unreasonable in the sense that he isn't concerned with utility.... he spends himself in pursuit of that passion, often to the detriment of himself.
But note, this is far from nihilistic, or some kind of random disordered madness, It is directed at achieving what he is passionate about. That ruling passion serves as an ordering principle of his instincts, whereas a villain like the Joker would be more of an example of someone where anarchy in the instincts rules, a degenerate in Nietzsches view.
Something else that comes to mind when thinking about these villains in Western Culture, it seems to me, is that the grotesqueness of some of these villains in part comes out of common tropes in Christian culture. In Nietzsches view the inversion of orginal noble values of good and bad into Good and Evil is not merely an exact inversion of these values but also a distortion. Moralising is distorting. Good didn't merely became Bad, but Evil.... a kind of demonization if you will.
What I think might be happening here with this sympathizing with these villains in Western culture is on the one hand a sense that we want to fantasize about setting free some of these impulses that have been suppressed in a Christian culture. But in doing so we still end up using these exaggerated distorted Christian tropes because that is what we are familiar with... because Good and Evil is the distorting binary we are used to thinking in.
Contrast this with earlier visions of the good life and self-mastery, where logos (reason) must order the lower appetites and passions. Logos has authority here precisely because it is:
A. Capable of knowing and desiring the Good.
B. Is itself a participation in a sort of greater Logos that perfuses and goes beyond the world.
In later modern narratives, there is first suspicion and the a denial that human logos can actually perform this function. This makes the old sort of narrative a sort of delusion and slavery that the villain exposed and transcends. — Count Timothy von Icarus
I've read your excellent thread on "Arguments From Underdetermination and the Realist Response", and I was planning to react to it but couldn't find the time... but I think what I had in mind is relevant here.
When you talk about "pre-modern" thinkers viewing things this way, I would want to say you are really talking about pre-modern thinkers after Socrates. In Nietzsches view Socrates and Plato were a break from what came before. Pre-Platonic Greece was Sophist, and reason was seen predominantly as another tool for convincing people, not necessarily to find universal truth... rhetorics rather than dialectics was the name of the game. The idea that we can arrive at truth by conscious reasoning, by dialectics was alien to most Greeks. At the time that was the radical idea, and the start of a complete re-evaluation of values (later picked up and spread by Christianity).
The logos is indeed often translated as 'reason' or 'the word', certainly in Christianity, but I think pre-socrates (and thus pre the Socratic re-evaluation of values) it had another meaning. In Heraclitus for instance is seems to me the Logos is more a kind of regularity, patternedness in nature that we can sense or intuit. Heraclitus was the opposite of a dialectician, not writing in arguments but aphoristically. He was very much advocating being more attuned to the logos, but reason was clearly not the way to do that. I think, with Heraclitus and Nietzsche, that we recognize patterns (the logos) by sensing and observing, not necessarily by conscious reasoning.
The danger for Nietzsche (and also someone like Adorno) is not necessarily that we are in the process of losing faith in reason in an absolute sense, as something that is necessary for every good functioning society, but that that happened to be a core part of the myth our particular civilization believed in, be it still under Christianity or after Christianity with the enlightenment. Because typically after the faith wanes, you get barbarism. Anyhow, Nietzsche believed all of this is more or less inevitable, because reason is a dissolvent for myth and faith, and so a civilization based on that will eventually eat its own tail. Realizing this, he felt compelled to become sort of an accelerationist, wanting to clear the old to make space for the new.