The co-chair of a task force set up by Harvard University to combat antisemitism has resigned. It was the latest blow to the university’s efforts to address complaints that Jewish students have felt increasingly uncomfortable on campus since the Hamas attack of Oct. 7. The co-chair — Raffaella Sadun, a professor of business administration — tendered her resignation on Sunday. She was appointed about a month earlier by Harvard’s interim president, Alan Garber. Dr. Sadun said in a statement on Sunday that she would continue to support efforts to tackle antisemitism from her position on the Harvard faculty. She did...