This is just a small detail I've noticed over the years, both in real life as on tv/movies.
Whenever a man is comforting someone, either by hugging them, rubbing their back, shoulder, arm or hand, I noticed that they nearly always rub their thumb against the persons back, shoulder, arm or hand. I've never really seen women do this. I"m just curious to know if there's a reason behind this.
And it doesn't matter whether the person that is being comforted is male or female. I always notice this detail.