China’s propaganda mouthpiece is in some ways just your typical, old-school news outlet, stumbling its way through the brave new world of social media. The difference from other newspapers is that from the perspective of the People’s Daily, losing control over the online conversation could have dire consequences.

In a lengthy essay published Monday, Yang Zhenwu, chief editor of the Chinese Communist Party's flagship newspaper, warned that Beijing could make a “historic mistake” if it fails to control new media and harness...