"The guy was immediately seen to be a traitor to China, especially by the way he smiled..."

No it isn’t. This guy was regarded as a traitor to China immediately he was seen, especially when they saw the way he smiled. The look on his face suggested he was lying or couldn’t be trusted.

It has a few problems. try saying: "The guy was regarded as a traitor to China, instantaneously obvious, especially when you see his way of smiling." the sentence is describing a traitor through the way they smile. hope this helps.^^