A Hongkonger has pleaded guilty to sedition over a T-shirt with a protest slogan on it, becoming the first person convicted under the city’s new security legislation. Chu Kai-pong, 27, appeared in front of Chief Magistrate Victor So at West Kowloon Magistrates’ Courts on Monday. He pleaded guilty to one count of “doing with a seditious intention an act or acts that had a seditious intention,” under the Safeguarding National Security Ordinance, known colloquially as Article 23. Chu was the first person charged under Article 23, according to HKFP’s records. He was arrested on June 12 this year a…