Not being an opera fan myself I will take their word for it:
Classical concerts comes with a set of very strict rules for the public: you cannot applaud while the music plays (the only exception being after opera arias), you are supposed to dress up, and there should be complete silence from the audience during the performance. And that urge to cough should be repressed until an applause. Yet, it turns out that coughing is more frequent during the performance.
Concert etiquette demands that audiences of classical concerts avoid inept noises such as coughs. Yet, coughing in concerts occurs more frequently than elsewhere, implying a widespread and intentional breach of concert etiquette. Using the toolbox of (behavioral) economics, we study the social costs and benefits of concert etiquette and the motives and implications of individually disobeying such social norms. Both etiquette and its breach arise from the fact that music and its “proper” perception form parts of individual and group identities, convey prestige and status, allow for demarcation and inclusion, produce conformity, and affirm individual and social values.
See also: Miller and Page on the “Standing Ovation Problem”