Porsha Sharon, 28, still thinks about the outbursts she witnessed from customers she served last year at Buddy’s Pizza in Troy, Mich. One woman entered the restaurant and simply ordered a pizza, to which Ms. Sharon responded, gesturing at the extensive menu: Which kind?“Did you not hear what I said?” the customer replied, according to Ms. Sharon’s recollection. “Are you dense?”Other customers mocked Ms. Sharon for wearing a mask. The eight-hour shifts ended with burning pain in her swollen feet. She got an offer in March to start working as an administrative assistant at a law firm, work she did on a temporary basis in college, and last month she quit the pizzeria.“The las …