Deleting a user in LOVD is a non-permanent action. Since the user may have created or edited variants, patients, custom columns, custom links etc, permanently deleting the user from the system may leave some references in the database broken. Therefore, deleting a user only disables the user's account and removes the user as a curator from the genes he or she was a curator for, but does not permanently remove the account. A deleted user can therefore be 'revived' by editing the user and unchecking the 'deleted' checkbox.
If the user is the only curator for one or more genes, and you delete the user, you inherit the curator rights on these 'orphaned' genes. If you want to prevent this, make sure the gene has at least one other curator.
From the user's detailed view, a link named "Delete user" is available if the user has not already been deleted and you have the correct rights on the user account. After clicking that link, you need to confirm deleting the user with your password. Also, if you will take over any genes, this is reported on this confirmation form.