City of Bones
How we cite our quotes:
"[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.
"I don't like flat soda. I don't like crappy boy band pop. I don't like being stuck in traffic. I don't like math homework. I hate Jace. See the difference?" (17.119)
Simon clearly never heard '90s boy band LFO sing "Summer Girls" or that might put his hatred for boy bands in the same, or higher, category than his hatred for Jace.
"I've never liked any of your girlfriends, but at least I've had the decency to keep it to myself." (17.122)
It looks like the time for decency has passed. Air that dirty laundry, Clary!