“Microsoft Authenticator will overwrite an account with the same username. Given the prominent use of email addresses for usernames, most users’ apps share the same username.”
Google Authenticator and nearly every other app add the issuer’s name to each account. Microsoft only uses the username, so scanning a new QR code can silently wipe an old one. Users find out weeks or months later and blame the company whose login stopped working, and that company’s helpdesk eats the hours. Complaints go back to 2020. The bug spares Microsoft’s own accounts.