Aiden was more excited that Danny was up for promotion than he was. Also, when Mac took off his gloves and told Danny he had the scene, I was surprised that Danny didn't say anything. No smart answer, joke or even a serious reply like 'you can count on me', absolutely nothing, like he was in shock.
Yeah, you're right. No excitment, nothing. And even though he's immature when investigating and always has to present his evidence first (saw him do this in "Tri-borough," too, last night to Maka) and is stubborn about pursuing the cases, we've never seen him have any real faith in himself. It's a strange kind of Catch-22: he doesn't really trust others (he's always doggedly pursuing his own hunches/evidence first), yet he doesn't seem to really be confident in himself.
Have you ever noticed how when Mac yells at him he kind of just stands there and takes it? He'll offer a weak protest sometimes, but mostly he just stands there and hangs his head. Most people are defiant and stubborn even when they know they're in the wrong, but Danny just kind looks like he expects to be yelled at. Or worse. He didn't express a single disappointment or protest at all when Mac told him he was off the promotion grid.
In the book, one of the case studies was a man who couldn't believe it wasn't his fault. The therapist gave him an account of a child being abused and asked whether the child deserved it. The man said 'no' and she asked him 'why is it any different from when you were a child then?'.
See, I could totally see Danny taking this stance. He would never, ever tolerate anything bad happening to a child in a case he was working on (I think he'd take it pretty hard, actually), but I think he'd see his own situation as different. He'd assume he was bad, the adult hurting him was just trying to "fix" him, etc.
If you think about Danny being yelled at by Mac, by Hilborne, by whoever, he always looks so defeated. Like it's not even worth fighting because he thinks they're right about him. Even if Mac was right about how Danny should have listened to him, the normal reaction still would have been for him to defend himself. But he didn't--he just stood there and took it. Did that strike anyone else as being off?