I have two users I would like to create a pseudonym for of the form fname.lname but when I try to create one it tells me the account already exists as a user-deleted account.
That means that you deleted that account in the past, and there were errors during the deletion. The server manager had a red "operation status report", which you didn't notice or ignored.
The correct thing to do is to study your logs to see what went wrong during the user deletion, and then fix that problem before proceeding. You can then manually delete the 'user-deleted' record from the accounts database:
db accounts delete name_of_account
[If you search here for 'user-deleted' you will probably find that this same advice has been given multiple times previously.]