After early previews and public testing were completed earlier this month, Microsoft officially introduced Cortana for Android devices on December 9.
Less than two weeks later, Microsoft pulled a key feature from the app: The latest update disables the "Hey Cortana" listening function on Android devices.
WinBeta noticed that Microsoft updated the software in the Google Play Store on Sunday. In the "what's new" section, you'll see three things: Improved app stability, enhanced call and text features and the "Hey Cortana" feature removed for U.S. market.
The likely reason for the removal may be Cortana interfering from Google's own "OK Google" listening activity. WinBeta noted that problem early this month, finding that Google Android phones with Cortana installed couldn't access their microphone to use Google's personal assistant software.
A manual fix at that time was found: Simply disable the "Hey Cortana" feature in the app. Now it seems like Microsoft has outright removed it so as not to cause problems for Android device owners that are used to using voice commands with Google Now and Google searches.
It's a good move on Microsoft's part to do so, but I'm surprised that this issue didn't arise during prior testing; either while in beta or preview modes. Then again, perhaps a code change in the final software version is causing the issue.
In any case, I suspect Microsoft will resolve the conflict sooner rather than later and Cortana for Android will be happy to obey your spoken commands.