Well, you yourself know that you’re not diagnosing anyone, so what is the point of putting a very specific mental illness label on someone? ‘Specially since you’d likely be wrong. Why does the specific label you assign really matter anyway in general social situations?
If a person with mental illness wants to talk about it and give people some ideas on the how are the illness affects him or her, and the best way to interact with him or her, that is a different thing.