Renaming and Deleting Users
Initial suggested best practices (in advance of the extensions being available for use):
1. When renaming a user, always select to rename the User and User Talk pages as well. If the user doesn't want those pages carried across, delete them after doing the rename (so that the deletion history shows attached to the user's new account name).
2. When merging/deleting a spam account or other completely bogus account, delete any existing User and User Talk pages in advance, and also check for any other pages created by user which would presumably also be deleted. Any pages edited by the user would presumably need to have the edits undone (or reversed manually if needed).
3. When merging/deleting a real user account into another account for that same person, be very careful if there are any existing User or User Talk pages for the old account. In some circumstances it may be better to merge/delete the new account into the old account, then rename the old account to the new account. Even better of course, if the user hasn't created the new account yet, is the straight rename.
4. If user just wants their account deleted, period, and there are no contributions, I see no reason not to merge/delete it into Zzzzzz. If there are contributions, merging/deleting into Zzzzzz are going to make those contributions appear to have been done by Zzzzzz. In this circumstance, I would suggest to the user to allow the account to remain and they just not use it any more. If they really, really, really want it deleted, then I guess still go ahead and merge/delete it into Zzzzzzz (unless we want to create some other account for that purpose if/when this ever happens).