Short answers, pulled from the story.
Søren Kierkegaard published Practice in Christianity in 1850. He argued that personal authenticity depends on finding an authentic faith and being true to oneself against bourgeois society.
Walter Kaufmann assembled a canon including Søren Kierkegaard, Martin Heidegger, and Jean-Paul Sartre to define existentialism for English speakers. These thinkers believed the conscious Self must come to terms with existence in an absurd world featuring external forces like thrown-ness.
Erich Fromm proposed a definition of authenticity in the mid-twentieth century that differed from earlier existentialists. He considered behavior authentic if it resulted from personal understanding and approval of its drives rather than conformity with received wisdom.
Users experience constant tension between projecting personal values and meeting social expectations to share popular values on social media platforms. Popular values are predominantly commercial and users engage in social media rituals like taking countless photos and carefully curating images of commercial experiences.
The authenticity of an artist has three bases including long-term dedication historical knowledge and personal integrity for correct choices. Black metal adherents value above all else artistic authenticity emotional sincerity and extremity of expression.