It depends on the relevant laws and regulations in Hong Kong. If Hong Kong law says that eating chicken feet by subway should be punished, then it should be punished. If Hong Kong law says nothing, then eating chicken feet is nothing. Eat it.

But in Shanghai, it is only stipulated in the passenger code. Obeying the rules depends on self-awareness, so if you don't follow them, nothing will happen, and it's not for other passengers to say anything. If other passengers say something, it is a provocative act and will naturally be insulted by counterattack.