Harry has literally been watching the current body Voldemort is inhabiting for the entire time that body has existed. He has seen every spell cast while Voldemort has been using it.
Either Voldemort has not raised shields (which he typically did not do as Quirrell) or he's capable of casting shielding spells which Harry cannot detect either the casting or ongoing effects of even in the midst of extended close observation. And if it's the latter, we're back to "in order to have a shot at beating someone, you have to assume he's theoretically beatable and act accordingly".
On the gripping hand, I'd more expect his new, permanently-transfigured body to just be naturally bulletproof, rather than conventionally shielded. But it's not helpful to believe he's actually thought of everything.
Shields are useless against Harry's magic because of the resonance. The earthbending trick was nice, though.
This is a new thread to discuss Eliezer Yudkowsky’s Harry Potter and the Methods of Rationality and anything related to it. This thread is intended for discussing chapter 112.
There is a site dedicated to the story at hpmor.com, which is now the place to go to find the authors notes and all sorts of other goodies. AdeleneDawner has kept an archive of Author’s Notes. (This goes up to the notes for chapter 76, and is now not updating. The authors notes from chapter 77 onwards are on hpmor.com.)
Spoiler Warning: this thread is full of spoilers. With few exceptions, spoilers for MOR and canon are fair game to post, without warning or rot13. More specifically: