Why did Joker show no signs of PTSD? SPOILERS
He witnessed Private Pyle blasting away his drill instructor with an assault rifle and then blowing his brains out all over the latrine. Then in the second half he is goofing it up as a military journalist like he has no post-trauma stress. If I witnessed a murder-suicide, I'd be horrified for years just as so many veterans that returned from Vietnam. Joker turned out to be the main character but we were more concerned with the Sergeant and Pyle.
Awesome movie though.