Most discussions around China's censorship practices focus on its filtering mechanism, the so-called Great Firewall of China. Yet there is another side of the story that remains unexplored: The virtual community management system that coerces social media users to censor themselves.
A recent report on the character of social media in China, conducted by the state-run Chinese Academy of Social Sciences, describes social networks as rumor mills  that are mainly used by poorly educated social groups.  The report has further justified the use of community-managed self-censorship practices.
Sina Weibo, China's most popular social media platform, introduced a community code of practice (CoP) in May 2012. A since-established CoP Community Center manages a demerit point system has been set up to punish users who violate its rules. The rules prohibit the distribution of commercial spam, indecent materials, and “rumors”.
The definition of “rumors” is very ambiguous in China. Any piece of news or information that has not been released by official government channels can be considered a rumor. For example, the outbreak of SARS  was first appeared as a rumor in November 2002. In cases when the government wants to suppress the news, all discussions are labelled as rumors. When Chongqing Public Security Bureau head Wang Lijun took refuge in the US Consulate,  information on his whereabouts had circulated online for over a week as “rumor” before the Chinese government confirmed the information.
According to the Beijing News  [zh], the CoP demerit point system is enforced by reports from users, a community management platform, a committee that reviews disputed reports, and credit and notification systems. Below is the structure  of the Sina community content management platform.
Each social media user begins with 80 credit points. When her credit is reduced to 60, the user will be considered a low credit member and will be subject to certain restriction in her use of the micro-blogging service. When the credit dwindles to zero points, the account is deleted permanently.
Over the past year, the CoP Community Center has received more than 15 million reports. Twelve million of these are related to commercial spam, 1 million to indecent material, and 2 million relate to the spreading of rumors.
Beijing News reported that once the center verified a rumor, it would delete the rumor and issue a notification to all users who have received and distributed the “rumor” and tell them that the deleted message is a “rumor”.
The CoP Community Center has recruited 5500 people to review the reports in dispute. The center is planning to expand the censor team to 100,000. Team member recruitment takes place by invitation only. Whenever a report alleged to contain a rumor is in dispute, the center will select a subcommittee to review the disputed case.
Community Center Head Hu Yadong told a Beijing News reporter that within one year, the daily number of rumors had been reduced by 87% from 4,000 in May 2012 to 500 in May 2013. The deletion of content has already resulted in the migration of users from Weibo to other platforms such as WeChat , a mobile based group sharing platform.
In the future, instead of deleting the rumor, the system will add a “rumor” label to the message so as to strengthen the “rumor clarification” process. If the “rumor label” system is implemented, it will not only add transparency to the community content management, but also prevent the massive deletion of content in Sina Weibo. But it remains to be seen exactly how the system will work, and how it will be applied to messages of a political nature.