It works for me too. When I search for 'office365 twitter' the official MS Office365 Twitter account is the 1st result along with several other links to Twitter. Maybe it's a regional issue?
DDG gets results from Bing, try it too.
Doesn’t work in bing too!!
Bing blocked your IP address, use mobile Internet or VPN.
If I search from my phone (with the query “codinghorror site:twitter.com”) I get no results, but if I search from a tablet I see results as one would expect. Weird…