A Frequently Asked Question is, is it possible to delete user accounts from the Vault? The answer is: not at this time. The reason is that Vault keeps historical data, and user account information is attached to that data.
If user accounts were to be allowed to be deleted like they can be in Windows, fields such as "Author", "Checked By", "Current Owner", "Created By", "Checked Out By", "Engr Approved By", would be replaced by a randomly looking Security Identifier (SID). Not only is this unsightly, it would complicate the introduction of new features because "delete user account" special conditions would need to be addressed at the design, development and testing phase, ultimately slowing down the Vaults evolution.
It would also slow down the process of bug fixing.
If a spelling mistake was made during the account creation, weighing up the benefits, the easiest solution all round is to simply disable the account.
You can also rename user accounts, so you could disable it until you need it then rename & enable it for a new user. Its kind of like...virtual recycling :-)