I was wondering too. Extremely cryptic by Rowling's standards, that - generally she doesn't do that. My best guess is it refers to the manner of Voldemort's possessing Nagini, without necessarily implying he knows about the Horcrux already. A really cryptic way of saying Voldemort isn't an Animagus but just controls Nagini somehow?

Yeah, that was well done. It's also interesting in thematic terms how Harry knows things about house-elves Sirius never realized despite living with them his whole childhood - because Harry has encountered them in such a different way and seen a different side of them.

Yeah. One thrown into Azkaban, one in St. Mungo's and assassinated when it looks like he might start talking (though I guess Bode wasn't necessarily under the Imperius, perhaps he just caught them in the act at some point). The Death Eaters have still maintained their secret. Now Rookwood is about to be freed, so there won't be a third attempt until the fateful day.

Incidentally, it seems quite likely that times like these are when Lucius' gifts to St. Mungo's come in handy: he gets inside information on patients of interest, thus allowing timely action.

Yes, I was thinking of your comments about tragedies when I read that. It is a classic example. Though it's also a pet peeve of mine in books when characters for whatever reason refuse to even consider such a gift or note or whatever and throw it away or ignore it immediately for emotional reasons. Don't they have basic curiosity? Maybe I just don't have strong enough emotions, or too much curiosity.

Yeah. I'm not sure how to take the repeated charge that Snape is "opening Harry up for Voldemort" - obviously it isn't his intention, but it does seem to be the effect, and should he not realize that and take measures accordingly?

And adds particular meaning to the way Voldemort walked around his circle of followers and looked into all their eyes last book.

I believe so, we'll hear about it in the next chapter.