< For example would you expect a scale factor in x to apply to the world x axis, or to the horizontal axis on the 2D screen?
the "x" render factor is just apply on the 3D screen not in the 2D screen !
it's a visual factor, not a measure factor :)
2D view screen are real measures, 3D view screen (for these sorts of representation "false" measures: for printing for example)
not a prog (it's Illustraor) but something like that
http://www.portices.fr/formation/Res/DessinVectoriel/pTrimetrique.html
Result in the 3D view screen (print) can be "distorted" by the factor of "render"
Is that pertinent? I don't kow :)