Comment 2 for bug 699335

This is a known problem, and one which is actually quite hard to fix.

I'm looking into it when I get some spare time, and I believe the (initial) fix, will be to introduce code which clips away pieces of polygons which aren't thick enough to meet the design rules.

I don't know if this would be applied to "solid" polygons, so it would also be helpful to create a DRC check for too thin polygons. This will almost certainly require similar code to the above fix.