Some people who speak English well still have thick accents. Asking for clarification or inquiring about the accent isn’t national-origin discrimination, as long as it’s not disrespectful.
Recent case: Soon, of Korean national origin, works in health care. She has a Korean accent and her co-workers sometimes have difficulty understanding her. She claimed that one supervisor criticized her inability to say “odor” and “order” differently. Sometimes, in Soon’s opinion, the boss made light of her pronunciation efforts.
She sued, alleging she was the victim of national-origin harassment.
The court disagreed, reasoning that a heavy accent may interfere with smooth communication and commenting on the accent isn’t discriminatory unless it’s pervasive, frequent and offensive. (Park v. VA, et al., No. 14-1063, 3rd Cir., 2014)