The whole point of 'peacefull' stratification is is that everyone internalizes it 'voluntarily'. If they (the underclass) didn't, and realized their power, saw it was nothing more than custom holding them back, it wouldn't work and other methods would be invented. There is a reason Britons proclaim to be non revolutionaries, that is very much in support of their stratification.

Your observation that the subtle cues seem to be the only thing keeping the classes apart is precisely the goal. This way it costs minimal effort to keep the stratification in tact.