Argyle pattern anything.. this is Inner Mongolia, not bloody Gleneagles.A gala performance or first night maybe, or if one is a celeb, or is likely to be on TV. The performers don't care what the audience wears. In fact in most theatres they can't see much of the audience from the stage anyway, due to the bright stage lighting and the house itself is usually dark during a performance. They might care more if their singing and music is appreciated or not.
#3. Generally, underdressing for an occasion. One simply does not go to the opera in a polo shirt, but many men do. It is extremely insulting to performers to have their audience appear not to care at all about the event.