What is Hidden?
This is a feature that hides specific users from search results and message lists.
How you look to the other party:
The other party is not aware that you have set them to be hidden.
The other party can still send messages to you as usual.
Please note that you will not be notified if you receive a message from a user you have set to be hidden.
How to unhide?
Tap 'Profile'
Tap 'Various settings'
Tap 'Hidden/Block settings'
Tap the person you want to unhide and tap 'Unhide'.