So nobody @ MSFT has access to Google.com before shipping off the product. Given that a typical engineer is so addicted to 'googling' all through the day, this would've been noticed.
This problem just started in the last 24 hours - Google rendered fine and was my default search engine for over a month running the 8.1 RTM, and for a few months before that running the 8.1 Preview.
This isn't MSFT's fuck up unless Google is doing feature detection and IE11 is presenting itself as not supporting some trivial HTML5 feature.
Edit: I stand corrected - it looks like something MSFT pushed out as a compatibility list update around the general availability of 8.1 is causing this.
On the other hand, it's very strange that it suddenly occurred in the past day, when I've been running 8.1 release for over a month.
Anyway i also have a lumia but I set google as search engine in ie mobile