Okay. It occurs to me we have some inferential gaps that I don't see my duty to fill. Go read HPMOR again, go read some more sequences. This is beginner level stuff, you are not presenting strong-evidence-based arguments, you are asking rhetorical questions, making non-deep analogies and taking things literally.
Is there a "Magic" term is the True Causality Truth? Is there a "Magic" factor in the math from which Decision Theory is created?
There is not a term for "magic" anywhere because first of all, we are arguing about a fanfic, so let us get that mind projection out of the way.
I know Eliezer's core beliefs and messages: He will not allow his work to portray a universe where anything is inherently "magic" because that is bad reductionism. He will maybe not introduce a new kind of quantum mechanics, because it is very much not his style to techno-babble.
Broomsticks, for gods' sakes!
Broomsticks do not conclusively break anything. The speeds are too low for the gamma factor to be measurable with equipment that can function around magic. Broomsticks probably have maximum velocity only in the apparent. Remember, there has not in canon been any precise measurement of the nature of broomsticks.
That the physics is the way imperfectly thinking beings thing is not a credulous hypothesis, because QM and GR are experimentally right, yet counterintuitive, and because the program that describes Aristotelian Physics is more complicated than the QFT lagrangian, for any representation of rational numbers. I know the math, evidently better than you.
Likewise, someone thought that faux-Latin and wand movements should be required to lift stuff with magic, so they mostly are (obviously there was a dissenting opinion somewhere). Someone decided that Seeker was an interesting game rule, and someone decided that Hogwarts need not have a consistent internal layout, so all of those things are true enough.
Have you completely missed the chapter where Harry thinks that the "heart of magic" is a thing the Atlanteans built? In the most recent chapters he thinks about, and talks to Quirrel about how one goes about making a new spell!
Seekers existing does not have anything to do with magic, it has to do with the culture surrounding games. You can see it in many existing games and sports today. Wizards are still human, they have human habits.
Why are we even arguing? I agree to almost everything you say which is not a blatant argument soldier!
I don't accept that "strong evidence-based arguements" is a meaningful phrase in the presence of a counterfactual premise. If there was introduced some kind of unexplained techno-babble that wasn't consistent both internally and with the entire story (including the exchange rate of magical currency), it would simply be pushing 'magic' up or down the meta-scale.
The (reletivivistic) speed of a broomstick is roughly equal to the speed of the Earth, which almost has measured relativistic effects (GPS satellites in LEO observe relativistic effects fro...
Some people have been asking the question about the 6-hour limit on time turners in Harry Potter and the Methods of Rationality. Apparently, if a character, let's say it's Amelia Bones, goes back in time N hours and relays a piece of information about the future to another character, say Dumbledore, then Dumbledore cannot go back in time more than (6-N) hours.
The 6 hour limit is a useful rule to keep the HPMOR universe from becoming over-complicated with time travel, however several people have brought up the following objection. The claim is that Amelia Bones, by traveling back in time and saying that she has information she hasn't yet revealed, has already revealed information about the future in the form of Metadata: That the future still exists N hours in the future and that Amelia Bones was in it, etc. I will show, however, that this is not the case.
Imagine that Amelia Bones has traveled back in time from 1 hour in the future, but she is confused about the time after having apparated across time zones and mistakenly tells Dumbledore that she has information for him from 4 hours in the future. Call this Scenario A. Now imagine that the same scenario happens, but that Amelia is not mistaken about the time. Call that Scenario B.
The thing to note here, is that, from the informational point of view of Dumbledore, provided he doesn't have some additional side-channel information, Scenario A and Scenario B are indistinguishable. (In the same sense that being in an accelerating room is indistinguishable from being in a gravity field in General Relativity.) This is what I mean by "time turner meta-informational relativity." Provided that the act of arriving at some time and place with a time turner doesn't itself leak information about how far in the future you arrived from, meta-information about the future is not the same as information. The time-space coordinate meta-information conveyed when Amelia Bones tells Dumbledore, "I used a Time Turner and I have information about the future," is smeared out over the possible 6 hours. This tells us that meta-information cannot be the same as particular information about the future.
Additional consequence: From this, we can hypothesize that *any* time-indeterminate information conveyed to the past will be "smeared out" over the possible range of times, and that further backwards-time travel is limited by the closest possible value. So, if Amelia came from 3 hours in the future and related a piece of information that leaves it ambiguous if she came from 1 to 5 hours in the future, Dumbledore should still be able to travel 5 hours into the past -- provided he is not also in possession of information that lets him narrow Amelia's possible departure time.
Additional additional consequence: given the above is true, time turners can be used to empirically expose one's possession of such side information. I can imagine this being used for some clever deductive feat.
EDIT: To address some confusion about indistinguishability: 1) This is in the context of a specific point in space-time. 2) A given piece of information can only distinguish Scenario A and Scenario B if it's plausibly consistent with Scenario A but not Scenario B, or vice versa. So the paths of single neutrinos or configurations of air molecules aren't going to be able to do this. However, if there was a leak in a canister of a gas (let's say helium) at the time of Scenario A (4 hours in the future) but not at Scenario B's time, then there would be additional data available in the form of an implausibly large number of helium atoms in Amelia Bone's clothes.