While privacy is an issue on TikTok, I would say the more concerning stuff is that they are actively curating speech: they frequently ban content critical of the CCP, promote pro-ccp messaging, and also sometimes they harass journalists using information that has a somewhat reasonable expectation of privacy. There is a suspicion that they bump up divisive content, but that's harder to prove since obviously Facebook and Google do this too. But douyin does the opposite, it bumps up non-divisive content.