We now know that the design is being used as a brand identification theme, finding it on about half of Infiniti's current lineup and likely to spread to the rest when they are redesigned.
I consider visual brand identity cues a good thing. Many upscale brands have taken great care to devise them and retain them over many decades. In the past, brand identity was handled by the design of the grille (Rolls-Royce, Packard, etc.), but there is no reason why other areas of a car can't be used (Cadillac's late 1940s and 1950s tail fins).
I think what Infinity is doing seems a bit contrived and fussy. But the whole point is for it to stand out from the rest of the automobile crowd, so there isn't much to complain about, especially when contrasted with Lexus' assertive double-L grilles.
2016 Infiniti QX60
On this SUV, the kink is near the upper part of the window.
2017 Infiniti Q60
But on this sports car, it is farther down and stretched out.
2017 Infiniti QX30
The kink rides lower in this smaller SUV. However, the window shape is not involved -- the theme is carried out using a piece of chrome trim.
2018 Infiniti Q50
Here is the latest sedan version. The actual C-pillar is only slightly curved at the window, the kink effect being largely carried out via the chromed trim.