Apparently the mark is supposed to represent the Rabelle's Curve when Resonance Liberation is used. The mark expands and creates a wavelength pattern associated with the resonator's classification. Pic related is Chixia who's curve is Mutant defined as having a sudden spike in the middle. So the stars don't mean much. It's the length of the waveform that matters. 5* resonators seem to have a longer one. Same with resonators associated with sentinels.