Hong Kong outcry after masked thugs launch attack

It's literally the play book of police to infiltrate groups and if necessary cause havoc. This occurs the world over. Some police have rules similar to the rules of entrapment for more embedded actions (see the police in UK green groups recently) where they can't directly cause trouble but they can provoke and supporting. And this is what's documented and legally allowed! Ethically the world thinks it's right.

Where it gets shady is where they cross the line. There is often reports of protestors being arrested and showing their badge and going free...

Protestor groups do not have strategies to identify infiltrators especially non violent groups.

Some groups explicitly allow trouble makers to flourish like the black bloc where everyone wears black and mask to hide any trouble makers.

Far left? There's no far left actors in this story. China is an authoritarian, single political party country with a mixed socialist and capitalist economy.

If you want to link them to a two-dimensional, simplified political spectrum, they're closest to fascism.

I suppose Stalin was far left as well in your mind.