Better architecture than inheritance on Activities that implement posts

I have this following architecture for a few activities and a fragment that allow a user to post messages.

The messages have a Parent-Child relationship where a Parent post (a feed) might have child posts (comments).

I am wondering if this would be the proper architecture to implement the above requirements. There is a lot of data being passed back and forth between the activities, an EventBus, a Marshall object, and the client.

On a high level is there a better way to implement posts?