The ongoing U.S.-China trade fight, Washington's sanctions against Chinese telecommunications company ZTE as well as the arrest of Huawei CFO Meng Wanzhou were among the "sensitive" topics censored on Chinese tech giant Tencent's WeChat platform in 2018.
That's according to a report published Monday by WeChatscope, a team of researchers from The University of Hong Kong's Journalism and Media Studies Centre that describes itself as a group aiming to "make censored articles of WeChat's public accounts in China open access."
The so-called "public" accounts are those created by organizations ranging from government institutions to private enterprises, producing what WeChatscope's report termed "content similar to Facebook pages."
Using a computer program built to visit published articles multiple times over a period to record their contents, WeChatscope tracked more than 4,000 public accounts that covered daily news. The posts were flagged as censored if the program detected that they had disappeared from the platform, the report said.
"By the end of 2018, a total of more than 1.04 million articles were included. Out of these, roughly 11,000 have been removed by the internet censorship system," said the report's authors, Marcus Wang and Stella Fan.
A representative for Tencent declined to provide comment for this story.
The report did, however, acknowledge that the system built by WeChatscope was unable to track posts that had already been censored by WeChat's own system before they were published. The filter, they said, is based on a list of keywords "created and constantly updated by state censorship authorities, and then handed down to platform operators."
WeChat is China's most popular messaging app, with Tencent claiming a monthly user base of more than 1 billion people as of September 2018. While it started out as a messaging service, it has transformed into an app for everything from paying bills to hailing rides or even booking flights.
In its findings, WeChatscope said there were four official reasons that were typically offered for a post's removal: the original publisher deleted the post, WeChat removed it because it was found to violate a law, WeChat removed it because it was flagged by other users as breaking platform regulations, or WeChat blocked the original publisher for regularly breaking community rules.
The study found that 8,092 of the approximately 11, 000 articles flagged as censored fell under the category of posts that were removed by their authors — accounting for approximately 74 percent.
"Self-censorship is a common practice among internet users in China as online speech can easily bring them trouble," Wang and Fan said in the report. "Users will often remove their own posts if they receive warning from senior colleagues or employers."
In a follow up conversation over email with CNBC, a representative for the WeChatscope team said the program had yet to develop a "solid argument on self-censorship" as its research was mainly focused on systematic censorship.
"We detected articles related to certain highly censored topics which were also collectively removed by public account users. For instance, the issue of (the) US-China trade war," they said. "In some cases, we would be skeptical to those self-removal cases that might be under pressure of overarching political censorship. However, we have to examine on a case by case basis."
When asked about the possibility of posts being removed by their authors due to an error, WeChatscope acknowledged that it had "observed news articles that were collectively removed by authors because of misinformation."
Beyond its WeChat platform, Tencent also made headlines on Monday for being an investor in social network Reddit's latest series D round.
Tencent's involvement in the fundraising round was particularly notable. Not only is Reddit blocked in China, but the platform is known as a bastion for free, unedited speech. Tencent is also a big investor in Snap, another social network banned in China.
News of the Chinese tech behemoth's investment in Reddit triggered concerns among users that the platform could become subject to the same kind of online censorship that takes place in Tencent's home country.
Yet, others argued that those concerns are overblown.
In a piece following the fundraising announcement, TechCrunch said: "Tencent is no 'architect' of China's Great Firewall internet censorship program. It's one of a number of companies which, from its success, finds itself a prominent target for the government with little room to wiggle out."
— CNBC's Arjun Kharpal and Julia Boorstin contributed to this report.