HONG KONG — The police arrived at the University of Hong Kong around 3 p.m., wearing black vests marking them as national security officers. They cordoned off the offices of the student union, combed its interior and seized several bins of material.A top police official said they were investigating the union over comments from its leaders that the authorities said had glorified violence. But the underlying message of the mid-July raid was clear: The authorities were clamping down on the city’s universities, and in particular its student activists.Students were among the most determined protesters during Hong Kong’s …
