A report in Ming Pao, a Chinese-language newspaper in Hong Kong, said the disappearance of Kong Qingdong’s account on Friday was probably due to his reply the day before to a person who claimed he was a soldier in 1989 and said the armed response was necessary to protect the government.

“Nonsense,” Mr. Kong wrote, according to Freeweibo.com, a site that collects deleted Weibo messages. “There was no riot. It was just framing them after you bloodily mowed them down. Can you name one student who was rioting?”