BangPatterns is a normal language extension to have enabled, was this used heavily? (hint: it's not enabled on "every source file.") You listed two of 28 files there, I'm assuming to try to show that the vast majority of the code in that repository is in the IO monad? You went from "vast majority" from one file to now two files. I'm looking for objectivity here, as you seem to be into. Let's see some numbers. I think anyone that glances at that repo would need some convincing of your claims.
Render.hs is 211 of 5580 lines of Haskell in the repository, by the way.
Curves.hs may not have BangPatterns but it is heavily in the IO monad. My point is sufficiently supported by the provided evidence, even evidence provided by you, exceptional cases not withstanding. Thank you.