Quote 1
"Down the rabbit hole." (6.20)
Jace's allusion to Alice in Wonderland proves that Shadowhunters do read books by mundie authors (assuming that Lewis Carroll was actually a mundie), and that he's about to lead Clary into a world that is both similar to her own and radically different.
Quote 2
"Let's not be hasty." Jace was actually grinning, the bastard. […] "[Simon's] cute like that. Look at his little pink nose." (13.115)
Even the third-person narrator thinks Jace is being a "bastard" for teasing Simon. And when the narrator thinks you're a jerk, well then you know you're on thin ice.
Quote 3
"[Simon] just looks dim-witted. Really his intelligence is quite average." (13.215)
Jace is so jealous of Simon, he can't resist making sarcastic digs at him even when Simon's no longer human. But seriously, what's Jace's beef with the guy, besides the fact that he's Clary's bestie? This makes it clear that, as awesome as he may seem, Jace is not the most mature of folks.