Developing a plugin allows users to hide content from other users by using BBCode.
Add the following BBCode to your post:
[LOGIN]content to hide[/LOGIN] : hides the content from the non-logged in users
[LIKE]content to hide[/LIKE] : hides the content until the user likes the post
[REPLY]content to hide[/REPLY] : hides the content until the user replies to the post
Discuss this on our forum.