I think they’re a symbol of understanding for sure. I remember compton pointing out garam’s scar as a sign of kinship because it was to show that he’d understood garam in the aspect of them sharing the same professor and wearing the same scar from the same man, and I find it similar to the way garam had felt about heejae’s scar above his eyebrow and that being a really big turning point in understanding heejae more. I think it is him realizing the pain he caused too

Are those scars actually visible? Because throughout the story no one has ever pointed them out or noticed them on any of the four, I always thought of them as symbols for the pain he inflicted upon them by how he treated them and forced them to hate him, does this mean that this is the starting of Heejae noticing what he has done and how much pain he has caused?