We are using SharePoint 2010 that has User sync set up with Active Directory.
Frequent problem that we have is that if an user comes to our firm with a name John Smith, we give him an user name jsmith. If this user leaves our firm we delete this user in AD. This does not delete the user in SharePoint (I'm not sure if they can be delete at all). After that if a new user comes with name Johanna Smith, we can accidentally give her the same user name jsmith. This causes a wrong connection in SharePoint and she suddenly logs in as John Smith which is completely wrong. The only quick solution I found was to modify the user data using power shell and turn John to Johanna (I know this is the worst solution).
We modified her username to josmith, but this did not help us. Can we create a new SharePoint user and connect that user to the right AD user?