You've done a fantastic job of describing what I couldn't put my finger on! One of the issues I had when developing this code was what I referred to as a "jarring" noise when distortion gain was turned up. It's like you describe: almost "metallic." I alluded to the "jarring" sound in the article, and it's great to know the culprit! There weren't a lot of repos, articles, or forum posts that had examples of solid, straightforward distortion implementations, and now I can see why.

Hopefully, we'll see someone get some code out there that helps clean this up!