However, there is a work/around. If the plane has an even number of edges, like a rectangle, then you can define the contour line, then define a plane consisting of the two shorter sides and two diagonals, and lastly the plane consisting of the two longer sides and two diagonals.
In this way, every line has been used twice and they're no longer green!
"Faceting complete!"
However, Stella won't accept a faceted polyhedron consisting only of infinitely thin planes: somwhere there has to be a closed volume.
Here's an example:

When you create the faceted polyhedron, Stella asks you whether coplanar faces should be blended - you have to answer NO to this, otherwise your planes disappear!
Here's the result:

My latest use for this trick was in using Stella to test the feasability of a three-dimensional construction. Currently I'm working as a volunteer in the Ethiopian highlands, where it's often minus fifteen C at night, so people can get pretty cold. As a woolcraft worker, I've been helping them to work out how to turn their sheep's wool into comfort and income.
That means making spinning wheels, which is tough for people with no wood and no woodcraft. We tried making wheels of grass, like baskets, but we're a bit too high up for that kind of grass so not enough people have the skill.
We've been "importing" plywood for making hand carders, so perhaps we could make wheels of plywood and string?
At 11 000 ft above sea level, Great Stella helped me to check the feasability! This wheel started out as a three-step faceting of a twenty-four sided prism. It works!

