This is an interesting question. In Blockchain everything is decentralized. Anyone has access to view anything. We will be able to impose encryption but most of the things are kept open for everyone to view. There are both advantages and disadvantages in this. 

The main advantage is that nothing can be hidden from the world. If we need a piece of information, it will be somewhere out there. We can always lookup. Due to this fact we will not be able to delete any transaction or broadcast in Blockchain. It becomes permanently available. This can be said as a disadvantage in a way but the weightage for it to be an advantage is more. That is why it takes a lable decentralized. 

We will be able to hide a particular post or comment from visibility by adding a commit in top of the previous commit.  If someone queries in the back end the previous version of the content will still be available but only the latest commit or broadcast will be visible in the UI.