So I'm a Spider, So What? - Kumo Desu ga, Nani ka?

[DarthEnderX]

Sophia mentioned "Don't give me that no-killing crap considering how many you've killed." Seems like Oka has been playing world-police when she tried tracking down all the reincarnators with power and determining whether or not they were "suitable" for the world etc.

Oka has administrator powers though, so she's likely working with them directly. So I doubt whatever she's doing is that simple.

See the game Vampire: Masquerade where you lose a bit of humanity each time you use your vampire-abilities.

That's not really accurate at all.

Vampire abilities don't affect your humanity at all, it's what you do with them. Vampires have a "Beast" inside them, and as they do more and more inhuman things, they become more animalistic in appearance and behavior. But that actually has little to do with "being human" because there are alternate morality codes that a Vampire can follow that will also prevent you from decaying into an animal that have COMPLETELY different behavior requirements, and actions, like murder, that would cause you to lose humanity on one path, don't on others.

Don't say "most" if your prime example is something like Slime

I gave FIVE examples...

Most isekai is the MC getting summoned or reborn as a human

Well MOST isekai are fucking video games, where the monsters aren't actually monsters, or people. They're just computer programs.