At the time I went through a laborious effort for a Reddit post to examine which of those negative prompts actually had a noticeable effect. I generated 60 images for each word in those cargo cult copypastas and examined them manually.

One that surprised me was that "-amputee" significantly improved Stable Diffusion 1.5 renderings of people.

If you don't mind, could you share the link to your Reddit post? I'd love to read more about your findings.