Look, here it is. In the circle, a small, forward angled cut-out at the base of the C-pillar.
It's named after Wilhelm Hofmeister, then BMW's director of design, and is meant to suggest that BMWs are rear wheel drive.
So why has it been dropped? Because BMW are bringing out a front wheel drive car - the i3 - which, as well as having no Hofmeister Kink, sports a floating roof. Basically they've avoided the subject of not having to put the Hofmeister Kink in by having no C-pillar at all.
Here's the i3, as captured by www.germancarforum.com
So now you know what the Hofmeister Kink is and why it's significant that BMW have opted not to include it. The website www.newmediacampaigns.com put together this handy image which shows the Hofmeister Kink in action on all BMW compact executive cars since the 1500.