You can assign the rights in the access control to one user only, i.e., limit to 'author', and assign the post to that user. You can also leave the authorship and assign to any number of additional individual users. See the 'Grant' tab when editing or creating the node.

The real power and convenience comes when using the user 'Roles' feature to assign rights. 'Roles' are like groups or types of users that automatically get to do whatever that type of user can do when assigned the role. Users can have multiple roles. The role with the highest permissions takes precedence, when multiple roles apply to an action under consideration.