JCR doesn't not have the concept of a "user" (unlike a traditional database for example). It has the concept of user credentials, which are a combination of a userId and password and the concept of permissions which are a combination of principals and privileges.

How you set up the authentication for a particular repository - i.e. the external system or abstraction which holds the actual users - is not part of the JCR API concept.

So the short answer is no, ModeShape (and JCR) doesn't have the concept of a user.