I would imagine you would add what @baris mentioned in here:

https://github.com/bubundas17/nodebb-plugin-hide-contents/blob/master/library.js#L19

if user is member of the poster set, return content as is

Hi,
I am finding a plugin for nodebb which will allow authors to lock/hide snippets of the post. and the reader/user need to do Certain actions (like replying to the post, Paying points, etc...)in order to gain access to the locked/hidden snippet.