Bon Iver is the alias of Justin Vernon, who holds an unusual place in music as both a singer-songwriter in an acoustic idiom and a collaborator with the biggest stars in pop, including Taylor Swift, Charli XCX, and Kanye West. Bon Iver’s new three-song EP, titled “SABLE,” is his first record of his own songs in more than five years. Vernon rarely gives interviews, so this is an extended version of his conversation with the staff writer Amanda Petrusich. They touched on the meaning of “sable,” a word that can refer to mourning and darkness. Vernon is not altogether comfortable with the acclaim he has received. “I’m not, like, famous on the street, People-magazine famous, but . . .  there’s been a lot of accolades,” he tells Petrusich. “I was getting a lot of positive feedback for being heartbroken and having heartache and I’ve wondered . . . [if] maybe I’m pressing the bruise.”