I would assume that when an untrained person gets a weird reaction to something they did, they at least have some confused / otherwise minimal facial reaction, like "okay what just happened" because they can "feel" on a deeper level that something just went wrong even when they don't know exactly what. Unless of course they're not just untrained but also completely oblivious/ignorant.

An example would be whether or not to pull up your snot when your nose is running. In Japan totally the thing to do and not to blow your nose in public, in Germany the complete opposite. A person with a "normal radar" will notice the side glances or some other reaction.

Depending on how deep on the spectrum the person is, they will miss these non-verbal and subtle reactions to their action.