"At that time, I felt that anything was possible." Li Xiaojia, the former CEO of the Hong Kong Stock Exchange and the founder of Diguantong, recalled that when Hong Kong's sovereignty was handed over in 1997, he and a group of returnee friends from the mainland gathered in Lan Kwai Fong, watching TV. The five-star red flag in the hall rose slowly in the rain, and they sometimes sang and sometimes wept. At that time, Li Xiaojia was the head of Merrill Lynch's China business, and felt like a "lucky man of the times" – he returned home after his…