Merits can be public or hidden. You can make a Merit hidden by clicking "Hide Merit" within the menu. Hidden Merits are only viewable by the Admin from the Org that sent you the Merit, and also cannot be shared through social media.
Permanently Hidden Merits are sometimes created by Orgs and function the same as normally hidden Merits, but can't be unhidden by you. Hidden Merits are denoted with an “eye with a slash” icon on their Merit card and are partially greyed out.