Managing user account names with spaces that stop the in app bell icon notifications

Summary:

We have users in the application that have blank spaces within their user account names due to multiple first or last names (e.g 'Mark John.Smith')

This causes the in-app Bell icon notifications to stop functioning (BPM worklist & email notifications not affected)

We have the User Name Generation Rule set to - 'FirstName.LastName'

If other organizations are experiencing this behavior - we are looking for ideas / suggestions how you manage new user name value edits before the new person logins in and transacts

Once a new user logs in a transacts, it's difficult for us to then edit the user name as it breaks the audit path of the transaction