As they talk, the person’s mouth will wobble in unexpected ways. One side of the mouth rises up higher than the other, causing partial snarls to form during and between words. The mouth shape will generally be dynamic, and can shift asymmetrically from one side to the other in the same second. This activity is entirely accidental and uncoordinated.
This signal shows a psychology that is actively making private ethical judgments about the statements they are articulating. At this moment the person is holding a very specific emotional opinion about the subject, and is pinging their emotional register for that opinion (which causes these contractions up toward the nose). Heavy use of this signal will reveal a person who is unapologetically opinionated and forthright about what they disagree with on an ethical basis.