The suit.
It bothered me that the suit is basically spandex... I guess they are being faithful to the source material... but it was very lame... he doesn't even have protection from small knives.
shareI think it's partial armour coverage. In the scene where he's going after Two-Face and he's running over the tight rope, he takes a shot dead to the chest. That shot rips the bat emblem up and reveals some kind of body armour underneath.
From that scene and the scene where he gets stabbed, it's safe to assume he's wearing armour plates over some parts, but that he's opted to have more flexible material for ease of movement. I loved the way his fighting style in this film was shown to be largely based around dodging and sneak-attacks (which require ease of movement).
A final note: from what I've read on the subject, body armour that protects against bullets does not necessarily protext against knives. So, he might be partially bulletproof, but have no protection against knives.
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I always thought the Joker was only able to stab Batman because he lost control and got too close.
An opinion is not offensive just because you do not agree with it.