Renaming username in JIRA will break the application it links to

Summary

In JIRA 6.0, renaming a username is not possible when JIRA is used for User Management. However, there is a method for changing username; which is to disable the JIRA server temporarily, change the username, and then turn it on again.

This creates a problem with 2 conditions:

1. Without Incremental Synchronization, a new user will be created, rather than renaming the username.
   
2. With Incremental Synchronization, no new user is created. But the pages that are created using the previous username will be changed to Anonymous.