From China Digital Space
dāngjīn huángshang 当今皇上
Allusion to the sitting president of China in general, and at present to Xi Jinping. Implies that the head of state was anointed, not elected, to a position far more powerful than "president."
In a September 2014 speech, Xi Jinping touted "consultative democracy" as a way for Chinese citizens to participate in government without elections.
Example of "reigning emperor":
Yushenghai (@余胜海): Crazy "Steamed Buns": Ever since Daddy Xi ate at Qingfeng Steamed Buns on Yuetan North Road, this classic capital restaurant has become a national sensation. Demand has outstripped supply for pork buns and stir-fried liver. Yesterday's everyday buns have become today's tribute to the reigning emperor. (January 24, 2014)
Throughout most of Xi Jinping's first term as Chinese president and CCP general secretary (2012-2017), commentators consistently wrote about the massive amount of personal power that the top leader appeared to have gained, commonly comparing Xi to former strongman leader Mao Zedong, and highlighting the imperial cache of control that he appeared to have gained over the state and Party. As the 19th Party Congress—the event that marks the transition from Xi' first term as CCP general secretary to his second—was beginning on October 18, 2017, The New Yorker's Jiayang Fan highlighted the "consultative democracy" of Party Congresses generally, and compared Xi's wealth of power to the "absolutism of emperors" of the dynastic era.
At the beginning of the 19th Party Congress, it became clear that Xi's name would likely be immortalized by being amended into the CCP constitution alongside Mao's and fellow formidable former top leader Deng Xiaoping's. This lent a credence to the ongoing comparisons of Xi to his relatively power-laden predecessors.
CDT first detected that "reigning emperor" was blocked from Weibo search results on August 21, 2014. It remains blocked as of October, 2017.