The Jawline
Feels weird, looks good. That's the whole idea.
Cameras flatten a three-dimensional face onto a flat image, and your neck and jaw usually take the hit. Stand normally in front of a lens and the soft tissue under your chin pools backward, which is where that "the camera adds ten pounds" feeling comes from. It's not really about weight. It's about posture.
Lead with your forehead, not your chin
This is a cue my mentor taught me years ago, and I still use his exact wording with almost every client: bring your forehead toward the camera, then drop your chin down just a touch. If I ask people to just "push your chin out" instead, they tense up and it looks strange. Leading with the forehead gets the same result, a jawline that's pulled taut and separated from the neck, without the awkward stretch.
Why it matters for your headshot
That's what gives a headshot its sharp, defined jawline - skip it, and everything just blends flat together. It's a small move, and yes, it can feel a little exaggerated in the moment. It reads completely differently once you see it on screen.