The comments in the com.sun.openpisces.Stroker.computeOffsetQuad() method talk about analyzing 4 points, but a quad only has 3 points.  They appear to have been copied from the Cubic() version of the same method without adjusting them for the new analysis of the 3 points in a quad.

Those same comments were copied to the native Pisces rasterizer in Stroker.c.

The same comments were also copied to the Marlin version of the file in com.sun.marlin.Stroker.computeOffsetQuad().