Also the fact that when you ask your login to be remembered the will just show you the email at the next login, without telling you if it's the personal or work account.
It is the worst login experience Iv've ever had, bar none, I am constantly amazed how they could ship that and always wonder what hellish dungeon of reasons there must be behind the decision to keep it as it is.
Yes, this can be confusing.
So you can have two accounts, say for (vimslayer@contoso.com, Microsoft Account) and (vimslayer@contoso.com, Contoso AD) - and there is no collision and no possible confusion on the system end. All the confusion is on the human end.
And there is a lot of confusion on the human end :)
However your organization may then do a deal with MS for Azure, or MSDN subscriptions, etc. And they’ll issue a login with the same email* address you@work.com — you now have two accounts tied to the same email, one which you created by yourself and one which your IT department created for you. There’s no way for you to change this second one. Typically authentication for the second one will happen via your org’s single sign on.
So the answer to “is this account personal or issued by your IT dept” really means — did you create the account yourself? Or was it provisioned for you by IT?
* Many orgs by default don’t use email to log in. Instead a “username” like jsmith is used instead. However while interfacing with Azure it seems to be a best practice to use email.