I've done this in the past. I've self diagnosed or outright lied about some of my diagnosis to seem "edgy" or "cool: in order to hide other diagnoses that I really had that would make me appear "weak" to people as a man such as depression, my reactive attachment disorder, and my borderline traits.

Before I took my extended break from PC in fact, I literally thought I was a narcissist because I read an article about vulnerable narcissism and I thought that I could relate to it so I used to be active on the NPD forums which was pathetic of me but I did also consider NPD to be more "manly" than borderline traits and depression.

Oh and about 3 years ago I thought I was a sociopath and told people how I was this badass ASPD and would lie about my hacking knowledge by threatening to ruin people's lives with my leet computer hacking skills and I would go making up crap about me having cousins in the Italian Mafia who could have people "taken out" to sleep with the fishies and other random lies all because I wanted to appear "tough" to people to protect myself from getting hurt.