I can upload an image that has spaces in the filename, but they do not render through the rewriting process.
If I upload: "Exploding red giant.jpg"
The source in the post becomes:
The file is uploaded (confirmed).
The image does not render.
Adding dashes to the same filename prior to upload solves the problem.
Even though I prefer no spaces in filenames, my users may not agree and this functionality should work right out of the box for them.
I may try to modify UploadController.cs to replaces spaces with dashes for the time being, until the rewrite is fixed (or until I am pointed to another solution).