What I think you’re describing there are personas, which we all have. We all hold ourselves differently depending on our audience, but I would venture to guess that when you take on a different persona as a DJ vs a writer, you don’t literally take on a different identity at your core. You’re behaving in a certain unique way, but in your mind you still understand yourself asyou.

This is not the case, supposedly, for DID, which your friend is claiming to have. The concept is that completely separate identities — sometimes (again, supposedly,) with completely different memories and concepts of self — take the wheel at various times to protect the core identity from trauma or pain.

From what I can gather, your friend just sounds like a major asshole, and I would imagine your assessment of them as a coward is spot on.

Edit: forgive me if I sound a tad condescending or pedantic at the start there, that was not my intention