As a purveyor of userstyles, I found myself wanting to change a tiny thing here or there on various sites without giving them each their own tiny stylesheet. I also didn't want to start adding random selectors to a global stylesheet and identifying them by comment; I wanted to identify sites by their domain, e.g. html.apnews-com and keep all styles for that site nested underneath. In order to do this, I think a userscript needs to be involved.
Keep on readin' on Add domain name to every site's root class list⟶