For whatever reason, my brother decided to adopt a really working class accent when he was about 17 - and at the time, I thought it was ridiculous. After fifteen years, I can see that it's not really just a silly affectation. It's actually him engaging with the culture he likes, and the people he likes, being who he wants to be. I don't really see anything wrong with that.
That's a very interesting interpretation of the situation, and I'll credit it. However I can't help but feel that purposefully affecting an accent like this is inauthentic, and untrue to your real self. I can see your counter-argument that, for your brother, this act is bringing him closer to his ideal self.
I also think authenticity is a strange bird at the best of times. Humans are basically defined by their inauthenticity. In the bible, the moment humans attain knowledge is also the moment they attain the art of lying, of concealing, of feeling shame for what they are and presenting something different. It's a deep part of how we see ourselves - that we represent things, ourselves included, to persuade, to play, to organize our thoughts.
There's something funny going on with our use of the word - we call some people and cultures authentic, while others are called insincere and affected - and I don't think it's strictly related to how performative a given culture is. Somebody could be authentically Italian, and that could literally mean they perform their life at a very high tempo.
