Dustfinger didn’t develop PTSD after Basta gave him his scars. He was able to process the experience effectively with the help of friends, and has always felt comfortable talking about it with Roxane. He experiences memories of the event the way one would expect, as traumatic, but has moved on and is no longer stuck there in a way that affects his daily ability to function.
However, he did develop PTSD after being read out of the book. Extreme prolonged mental, physical, and emotional distress was compounded by having no social support system with which to process the event. He was largely confused, alone, hungry, and afraid for years on end. During that period, he was also sent verbal and nonverbal messages by the only people he knew (Capricorn, Basta, Silvertongue, and the Black Jackets) that he was worthless and weak, causing him to stagnate, integrate those attributes into his sense of self, and create a mental block around healing. When he has nightmares and flashbacks, they are mostly about his first few days to years in this world. He has since developed other symptoms of paranoia, social isolation, and hypervigilance.