Depending on how you are authenticating you will see URLs with various words in them.
loginlive office.com outlook.office.com office365 outlook.com account.live products.office.com login.microsoftonline.com
and this list goes on and on... I am wondering if they made an announcement that they are fixing their messy authentication workflow instead spending resources in rewriting office in JavaScript, that would have gotten this much attention on hacker news.