Rename the user's Foswiki homepage in the Main web, such as from JaneSmith to JaneMiller.
Fix backlinks in the Main web only
Make sure the group topics are updated (if any.)
Edit the Main.WikiUsers topic and move the user's entry so that the list is in proper alphabetical order.
Recreate the old topic with a pointer to the new topic, so that links in other webs work properly. Example content:
%M% Jane Smith is now known as JaneMiller
If external authentication is used and you want to change the login username:
The login username needs to be changed in the authentication server (e.g. Active Directory)
In Foswiki's Main.WikiUsers topic, fix the mapping from username to WikiName: * JaneSmith - jsmith - 13 Sep 2006 to: * JaneMiller - jmiller - 13 Sep 2006
Removing User Accounts
The following form can be used by administrators to delete a user's account:
The user is removed from the user database.
The user's topic is moved to the trash web.
The user is removed from any groups.
Other topics like the users LeftBar are not removed.
Note: Consider leaving the user topic file in place so their past signatures and revision author entries don't end up looking like AnUncreatedTopic.
If you want to make it clear the user is no longer around, replace the topic content with a note to that effect.
The existence of the UserName topic should also prevent that username from being re-used, sealing the potential security hole regarding inherited permissions.