Comment 3 for bug 182832

create 2 paths with white fill and black stroke.
place them so that one partially covers the other.
select the one in the back, then the one in the front.

efffect->interpolate.
the preview shows that the new shapes are added frome back to front.

change which ever parameter you want in the effect dialog.
the new shapes are now added from front to back...

you can do the same with pattern-along-path: which shape is considered the pattern and which the skeleton depends on the selection order; this is screwed up as soon as you change a parameter.