GoodBoyDigital/pixi.js — pull request #730 by mowday (2014-05-02 12:07:09+00:00)
Title: Compensates for the pivot point to prevent it from altering the X and Y ...

I'm not sure how it's intended to work, but I don't believe the pivot point should alter the X and Y position of an object. It should only define the axle to rotate an object round.
Right now, setting the pivot point alters X and Y of the position.

Please see this fiddle:
http://jsfiddle.net/Mowday/b2jpK/
At first the object has a pivot point set to it's center/middle (0.5 * width, 0.5 * height).
This forces the object to be rendered outside of the stage as the pivot point has altered X and Y.

In the code I have added some parts you uncomment to see more examples of this behaviour as well as an example of the fix.