XF 1.5 Hide Thread until replied


I am looking for a solution to the following challenge
One of the reasons I use my forum is for learning purposes. I give people an assignment and they need to answer that before they can see what other people wrote.
I would love to be able to hide all posts and replies until a user created their own reply.
I did find: https://xenforo.com/community/resources/aayush-hide-hack-v1.1618/
But that requires to add tags in the actual post.

Any suggestions how to tackle this ?