Although it's possible that Snape is assuming that Dumbledore would't possibly forget to check for that (are there ways to check?). I know my first reaction to the original Rowling-fic is "OK, there's no way Dumbledore didn't know a teacher was being possessed by Voldemort."

In light of chapters 96 I would update this chance to 45 %.

re-reading chapter 76 made me realise the prophecy could not be about Voldemort at all :

Let's look at this prophecy in detail :

"The one with the power to vanquish the Dark Lord approaches,"

Vanquish, as Snape said, is a strange word to describe a baby accidentally toasting Voldemort, especially since we have evidence that this might not be what really happened. "Dark Lord" is used by EY quite loosely, and not as something specifically relating to Voldemort. Indeed, Dumbledore seems to worry that he could be this Dark Lord. Now, if we step outside of what we think we know about the prophecy...

Who is Harry trying to "vanquish" ? Who is it which Harry has "the power to Vanquish" ?

Dementors ? Death in general ? Dementors as an incarnation of Death ?

Could Death be considered as the Dark Lord ? I admit this is stretching the use of the word Dark Lord, but it does sounds interesting and more appropriate to Vanquish. Now, bear with me a moment and let's look at the rest of the prophecy : Born to those who have thrice defied him,

Now, while Lily and James have defied death 3 times, there's a million person in the same case on the planet. But WHO has defied Death three times in the Universe ?

The Peverell Brother. Harry's ancestors through the Potter Family.

Born as the seventh month dies, And the Dark Lord will mark him as his equal,

The Tale of the Three Brothers specifically says : "..."And then he [the third brother Ignotus, owner of the Cloak] greeted Death as an old friend, and went with him gladly, and, as equals, they departed this life." Harry having the Cloak works, as such. Alternatively, Harry "killing" Dementors make Death and he litteraly equals, in that they can destroy each other.

But he will have power the Dark Lord knows not,

The only unique powers Harry has are Dementor 2.0 and partial transfiguration Dementor 2.0 seems rather good.

And either must destroy all but a remnant of the other, For those two different spirits cannot exist in the same world.

I find really interesting that nowhere it is said that the dark lord "lives". "Destroy all but a remnant" could mean Dementing Harry, or Destroying all dementors except one, or giving Philosopher's Stones to everyone but without the death rate falling to zero (because accidental Death would still happen buit would not be an inevitability.

Note that this theory (still improbable, if I had to bet on it I wouldn't assign more than a 15 % chance for Death to be the "Dark Lord" of the prophecy) is still compatible with Dumbledore trying to trick Voldemort in a Dark ritual, or both of them interpreting the prophecy as in canon.

Despite agreeing with the rest of the essay (which is very good), this is not true. Tiresomely standard counter-example: "Heil Hitler! No, there are no Jews in my attic."

Depending on what it is that the other person disapproves of about me, I might feel annoyed or offended. But so what if I do? If I'm cooperating with a person to achieve something that's important to me, learning that he thinks one of my beliefs is stupid (for example) isn't going to change anything about my resolve to cooperate. Feeling otherwise would be foolish.

As it turns out, I have been called 'dogmatic' and 'fundamentalist' and various other charming adjectives because of my belief that an essential part of fostering the growth of a rational society consists of creating a social climate in which irrationality is seen in a bad light, and the best way to do that is conversational intolerance of unreason. I can't say I enjoyed being called dogmatic, but it hasn't affected my desire to cooperate with those I see as mostly rational enablers of foolishness. If I can get over my hurt feelings, why can't they?

Seem to be assuming there is a higher purpose for bullying, which seems to be making a mistake along the same lines as the parable of group selection.

Possibly bullies bully because they enjoy it and aren't stopped from doing so. What additional explanation is needed?

What about tolerating people who don't tolerate you? I think this calls for a tit-for-tat strategy.

Based on the original Newcomb Problem post, I would say this statement has a definitional, an empirical, and a normative component, which is what makes it so difficult to unpack. The normative is simple enough: the tools of rationality should be used to steer the future toward regions of higher preference, rather than for their own sake. The definitional component widens the definition of rationality from specific modes of thinking to something more general, like holding true beliefs and updating them in the face of evidence. The empirical claim is that true beliefs and updating, properly applied, will always yield equal or better results in all cases (except when faced with a rationality-punishing deity).

There is no such excuse as 'but I did everything I am supposed to'.

Huh?

Imagine a lottery with a $500 prize, 100 tickets sold for a dollar each. The rational thing to do is buy every ticket you can. But you get to the sales office too late, and one ticket has already been sold. You buy the remainder, but don't win the lottery. You ended up losing money, but you did everything right, didn't you?

Human speech is one of the most valuable resources in the universe, and he were are wasting it on things that convey no information.

It is not a scarce resource on the relevant scale. Water is valuable in the sense that you can do a thousand things, some essential, with it; this does not mean that flush toilets are an abomination.