After Moodle checks an external source and determines that a user has access, Moodle creates an account for that user in the Moodle database. Although Moodle looks to the external source for the username and password, records for the user's activity are kept in Moodle. The user's grades, blog entries, history and so on, are all kept in Moodle, under that person's username.
If the username changes in the external source, there will be no connection between the old username in Moodle and the new username in the external source. For example, if you changed a person's username in your external database from jsmith1 to jsmith2, Moodle would not know that the jsmith2 in your external ...
