Eh, how is it in the books? Is each book written from the perspective of whoever is the main character of that arc? And does the show adapt it as such? These are important questions I don't know the answers to. But the shifting perspectives thing is adequately explained by simple character interaction. There's more fanservice around Araragi because girls act more sexual around him. Like, why would Kanbaru be acting seductive if Araragi weren't there? As for Nadeko, we see another side of her because we see her alone. During her arc, in scenes where she is around others, she doesn't act any differently than she does in other arcs. Hanekawa and Senjougahara are completely consistent, since they are both stoic. One example I think Across brings up is how Araragi and Hachikuji interact when it's just them, that's it's sexualized because it's from his perspective. In the first episode of Second Season, when Hachikuji says how she left her backpack at Araragi's (deep symbolism for letting go, epic foreshadowing), Hanekawa thinks to herself that she maybe doesn't want to know the full story. Even when she is the narrator, she makes a joke about Araragi's behavior when he was the narrator. It's consistent.
As for painting that non-narrators with broad strokes, that's simply because it's not their turn. Those people aren't narrating. We don't get their inner thoughts on the situation. But the narrators perspective does not have any effect on the way things play out, just their presence does, basic character interaction. There's really just not enough evidence to me to support the idea that the world is presented from a shifting perspective. We may hear how the narrator feels about things, but the world is still presented from a consistent, external perspective.
That human tendency you talk about. The whole premise of the show is that we hide things from ourselves & others and that internal stress manifests itself in some way. A Freudian concept. Yes, we present ourselves to others not how we are. So they will only see what they are shown. I believe things of this nature are explicitly said at some point. Further evidence to me that the perspective is consistent, and character interaction accounts for any discrepancies.
What a bunch of words there. As for the humor, yeah, we'll just have to disagree. I don't enjoy a character telling me explicitly why the thing that someone just did was so odd, clearly for my benefit as a viewer. Araragi is the least funny. Kaiki is the most. If such info helps.
As for the fanservice, my main gripe is with those who try to justify why it's not fanservice or some such, which is a lot of people. So that doesn't apply to you, of course. And no, fanservice does not automatically make something bad, at least if we go with a broad definition of it. I don't mind sexuality in my entertainment. But some shows are more clumsy about it than others. When fanservice directly clashes with the tone of a scene, I don't like it. It has to feel like it's part of the show and not something tacked on. Also, if the character is compromised in order to accommodate fanservice, it ain't for me. I'm personally not a fan of the fanservice in Monogatari. It feels like the set pieces to me, very sterile and slick, hardly anything sexual about it at all.
That's going back to what I said about Brechtian vibes. Bertoldt Brecht was a playwright who essentially created the concept of the distancing effect, intentionally keeping the audience from getting sucked in and forcing them to view it from a more analytical perspective. You remind the audience they are watching a work of fiction by emphasizing the contrivances of whatever medium the work is in. Monogatari does this rather well, if that is its intention. The conspicuous editing, the surreal backgrounds, the fourth wall breaking, the lack of people other than the characters, it all removes me from it. So I can't even begin to be sexually titillated by any of the fanservice.
Well, I've said a lot of things. In the end, I don't like this show for various reasons and I think its fans are reaching too hard. It's not all bad, but you know, what is?