....I don't know I think it's cool

If you have someone who created it out of the blue because they want their character to do something then have it 'not count' since it wasn't the main host and no other reason then yea sure

But if there's a back story to it and it adds to the character I think it's interesting. DID is often put with stereotypes and such and when people role play a character with it but doesn't do those stereotypes I find it the most fascinating

Edit: also why I played a character with two alters. It can actually make a story deeper. Why do they have it? What event occurred? How much do they 'see'? How do they live with it.