How do I determine if someone has Dissociative Identity Disorder?

Your friend is wrong and you are right. He does not have DID. In DID the host personality is not aware of the alters. There is no possible way to even guess what he has if anything at all based on one text message.... maybe he just realized after he sent the text that it was rude or whatever and wished he hadn't sent it. DID happens when someone is subjected to repeated severe trauma in childhood (I was d by my father for the first time when I was 5. He continued to me and also sold me to other men to make money for college. This continued until I was about 10). I have 14 personalities and I was completely unaware of them until I was 41 and had been in therapy for 3 years for Bipolar and PTSD. Your friend is full of crap.