The Great Dodecahedron is my favorite polyhedron, and it's possible to build one out of paper. Give it a try when you get a chance !

https://www.polyhedra.net/en/model.php?name-en=great-dodecah...

The fact that f(L^2) is positive can be seen without inspecting coordinates: after all it is the length of e_i', hence positive.

Great article on stellated forms! I almost missed it due to the subtle unintuitive title!