The feature scores are from a paper cited on the site. The ranking features are proprietary to dissuade gaming but are a blend of open public data across a number of different sources.
I find it funny that all of these little tools lean into the slop = poop dynamic.
I'm building writetrack.dev - a writing signal sdk that helps folks understand proof of process. It takes a different approach to writing analysis and I'm pretty sure the logo will never feature a brown turd.