His edginess was hilarious and extremely in character and was indeed a big part of his character growth (and regrowth?)
It was in fact shown to be mostly an act and a way to escape who he used to be. Eventually found a good balance of edgy and hopeless romantic nerdy poet
I think the best edgy characters have good motivation for being asses to everyone and have some sort of redemption at the end that maybe softens their edge a bit. Holden is definitely one of them.
Dr. House from House MD is also an edgelord who is a fantastic charcter.