It has a clear interest in suppressing any adversarial views and is not bound by any laws.

Currently that interest is mostly confined to China itself, but I wouldn't be surprised about that changing.

I don't know how they could use that data currently, but they are inventive and usually use everything they can get.

Consider the recent stories where LinkedIn was used by China to recruit spies.

Now consider a person with health issues, whatever they may be. Many people can be turned by using their or their loved ones' health issues. Whether it's the money for health payments, promise of new treatments, organs transplants ... I leave to imagination.