> Auth with MS accounts is a giant mess.

It is indeed a giant mess.

If you go to live.com and click on the hamburger icon at the top, then under 'Apps' click on the "To-Do" app, you will be asked to enter the password for your work account, even though you are on live.com, not on office.com, and you are currently logged in with your personal account.

The only way to get past this is to click "use another account" then log in again with your personal account (even though you are already logged in!!).

This bug has been present for months now.