You must have a person in your portfolio of contacts on WeChat in order to interact with her or him. You cannot read about people you don’t know.
In the example of the timeline called Moments (for more about it read previous post), you will see the comments of your friend A and your friend B because both of them are in your contacts. If your friend B is not a contact of friend A, they will not see each other comment or like action on your picture.
This level of privacy is a huge protection against other users who want to know about your private life without asking you. This system provides a competitive advantage against Facebook.