He's quite the proper Englishman. 

Every opportunity can be a learning opportunity — even a One Direction concert. At the 1D show in Philadelphia this weekend, Styles spotted a disturbing sign in the audience. Initially  reading, "Hi! Harry. Your so nice," he gestured to the girl to pass forward her sign so he could correct it to "you're so nice." He signed and fixed the poster for proper grammar, making him a much more handsome and charming version of Microsoft Word's Clippy. 

Sources: Taelor Ford