Haha, it's kind of you to think of me, oh master of all things.
But to clarify, my formal background in psychology is in experimental psychology rather than clinical or developmental psychology. I did have many classes on both clinical and developmental psychology and did have exams on them, but it wasn't the thing my education was primarily focused on. More on stuff like understanding how an f-MRI works or what can be done with it or what the difference between face validity, construct validity and reliability are.
So while I know a lot more than the average person on the topic, I wouldn't really call myself an expert either. Incidentally, I also haven't really been following the conversation and took a sleeping pill which is making me a bit woozy atm.
That being said, I saw the topic of identity diffusion in one of my developmental psychology classes as part of Marcia's identity theory of how teenagers develop their identity (I think). In this theory there's four possible statuses your identity can be in based on two "spectrums" basically. One of commitment and one of exploration. These statuses are achieved identity, foreclosure, moratorium and diffusion.
I looked back into my class notes to be sure I wasn't full of shit and quoting (and translating) those notes it says: "Little room and space to explore, usually because of environmental pressure. Don't explore much and not in a goal-oriented way. Also make no commitment to a particular identity and often aren't actively seeking to. Often coupled with high anxiety, insecurity, problematic behaviour (like alcohol and drug usage), etc. Can be gotten out of through active exploration."
Unstable identity is also associated with stuff like borderline personality disorder.