In a statement, the Hong Kong police’s Cybersecurity and Technology Crime Bureau said he had been arrested because he was suspected of conspiracy to cause a public nuisance. He was released on bail, but the police said an investigation was continuing. Mr. Ip said he had not attended any protests this week.
Many of the protesters are college-aged and digitally savvy. They took pains to keep from being photographed or digitally tracked. To go to and from the protests, many stood in lines to buy single-ride subway tickets instead of using their digital payment cards, which can be tracked. Some confronting the police covered their faces with hats and masks, giving them anonymity as well as some protection from tear gas.
On Wednesday, several protesters shouted at bystanders taking photos and selfies, asking those who were not wearing press passes to take pictures only of people wearing masks. Later, a scuffle broke out between protesters and bystanders who were taking photos on a bridge over the main protest area.
For some, the most flagrant symbol of defiance came from showing one’s face.
On Wednesday, as demonstrators prepared for a potential charge by the police, a drone flew overhead. The protesters warned one another about photos from above, but Anson Chan, a 21-year-old recent college graduate, said she was unconcerned about leaving her face exposed, potentially revealing her identity.
Ms. Chan said she felt compelled to join the protests out of concern about the proposed law.
“Once people get taken to China, they can’t speak for themselves,” said Ms. Chan, who had traveled nearly two hours from Lok Ma Chau in northern Hong Kong to show support and hand out supplies after seeing scenes of violence on the news.
The mainland’s restrictions were on the minds of many.
“The bottom line is whether to trust Beijing,” said Mr. Tsui, the communications professor. “This is a government that routinely lies to its own citizens, that censors information, that doesn’t trust its own citizens. You can’t ask us to trust you if you don’t trust us.”
“These kids that are out there, all the young people, they’re smart,” he added. “They know not to trust Beijing.”