Part of the reason for Overwatch's popularity is that the game takes pains to flesh out deep and varied background stories for its stable of playable characters, and a character named Symmetra shows the game's dedication to representing as many different types of players as possible. According to Jeff Kaplan, the director of Overwatch, Symmetra is canonically on the autism spectrum, and some of her behaviors in the game reflect that.
Symptoms of autism spectrum disorder include difficulty picking up on social cues and a tendency to be easily overstimulated. During Overwatch gameplay and cutscenes, characters will often have canned dialogue with one another. Symmetra often returns other characters' teases with literal responses, showing that she doesn't understand the sarcasm behind them. Further, she often opts to focus on ordered defensive strategy rather than the chaos of offensive melees.