I think I can actually deflect this one by appeal to Actual Reality. (Some familiarity with quantum mechanics required.) Note that photons, by virtue of their momentum, have gravitational pull; yet in the quantum double-slit experiment, the gravitational pull of the photons is not enough to "collapse the waveform" as to which path they have taken. This seems to me to be exactly the same sort of "prohibited information" as in the fic. The best explanation I'm aware of for this is that the uncertainty in the quantities involved is high enough that, even though the photons' gravitational pull could in theory transmit information, in practice the resolution of the universe is simply not high enough for that to happen. The same thing could be at work here.
I feel like I just used a sledgehammer to kill a fly.
- This thread has run its course. You will find newer threads in the discussion section.
Another discussion thread - the fourth - has reached the (arbitrary?) 500 comments threshold, so it's time for a new thread for Eliezer Yudkowsky's widely-praised Harry Potter fanfic.
Most of the paratext and fan-made resources are listed on Mr. LessWrong's author page. There is also AdeleneDawner's collection of most of the previously-published Author's Notes.
Older threads: one, two, three, four. By tag.
Newer threads are in the Discussion section, starting from Part 6.
Spoiler policy as suggested by Unnamed and approved by Eliezer, me, and at least three other upmodders:
It would also be quite sensible and welcome to continue the practice of declaring at the top of your post which chapters you are about to discuss, especially for newly-published ones, so that people who haven't yet seen them can stop reading in time.