In all of my papers, I have attempted to include an indent-based hierarchy of the argument. Adding code-folding to this would allow for so much more detail here.

I don't think we should have papers being nothing but folds, but there is definite value in presenting proofs in this way.

One potential downside is that there is no longer an order that guides the reader through the paper. Because it isn't quite clear how deep the author expected you to unfold an argument.