What are reactions to trauma. How serious they can be and how many traumatized people really can cope. How unrealistic it is to show someone as traumatized and then fully recovered, and showing no signs that it ever happened.
A panelist was talking about how much more interesting she found the new Kirk, from the new Star Trek movie, with obvious trauma in his past -- and I piped up from the audience that sooner or later you want Wiley Coyote to have the Roadrunner for lunch because he's doing all the suffering -- unlike Tom and Jerry where Jerry can get hurt.
How your brain really does get hardwired differently after trauma, which is why people overreact; it's a form of self-defense. (LSD is showing some promise as treatment. A very, very, very controlled experiment.)
One audience member wanted to know how to make his traumatized characters realistic and some panelists said there was too much variety, he needed to do research, and another one said that something that is, in fact, usually useful: unreasonable behavior. Get someone's reactions out of proportion to the offense, and you can keep people intrigued until you reveal what the trauma was.