Hello, I only got one Windows Phone with the latest developer update but for it mootools reports
Browser.platform == 'ios'
The other values are correct: Browser.name == 'ie', Browser.version == '11'

The user agent for IE on this phone is:
Mozilla/5.0 (Mobile; Windows Phone 8.1; Android 4.0; ARM; Trident/7.0; Touch; rv:11.0; IEMobile/11.0; SAMSUNG; GT-I8750) like iPhone OS 7_0_3 Mac OS X AppleWebKit/537 (KHTML, like Gecko) Mobile Safari/537

In my opinion the reported platform should be 'winphone'.
Maybe others with (older) windows phones could check as well.

--- Want to back this issue? **[Post a bounty on it!](https://www.bountysource.com/issues/6434098-wrong-browser-platform-reported-for-windows-phone-8-1?utm_campaign=plugin&utm_content=tracker%2F22067&utm_medium=issues&utm_source=github)** We accept bounties via [Bountysource](https://www.bountysource.com/?utm_campaign=plugin&utm_content=tracker%2F22067&utm_medium=issues&utm_source=github).