[Inkscape-devel] Positioning of curves (and only curves!) differs from reference

While looking the W3C test suite I found that in Inkscape rendered versions of the files all curves seem to be (very) slightly offset compared to the reference image. And strangely enough this does not seem to hold for straight lines...

The first few color tests (with all the circles) show this behaviour for example, and especially color-prop-01-b is interesting as it shows both curves and lines.

Can anyone confirm this? Any ideas on why this is so? And who is right?