Regarding #2, I don't think either of those examples come up particularly in any of the main sequences, though they have been posted on (try the search bar on the right). As for the sequences, they are ridiculously intimidating at first glance, but worthwhile. My recommendation is just to dive in one post at a time (Mysterious Questions to Mysterious Answers is a good starting point, with plenty of real life examples), and not let the sheer volume scare you off. Don't make it a project, just take each post as something to read on its own.
Thank you Spurlock, that was helpful.
To expand on my previous idea: This is speculation not based on any direct evidence in the text, but I think the secret held in the Potion Book is the recipe for the potion Lily used to turn her sister beautiful. EY points out several times how Transfigurations are dangerous, points out that this is why there are still fat people etc., and Petunia herself describes the process as very long (sick for a month). So it might be possible that the potion uses Dark Magic or some other terrible secret was involved in its creation.
ETA: There is now a third thread, so send new comments there.
Since the first thread has exceeded 500 comments, it seems time for a new one, with Eliezer's just-posted Chapter 33 & 34 to kick things off.
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