Mottie Author

data: URI's could pose a DMCA risk.

Almost all userstyles are below 100KB (ref) and therefore limit their use of URI encoded images due to the restrictions set by USO. You could impose a no-URI restriction if it is that much of a concern.

putting CSS directly into a tag and injecting in via a .user.js is fairly simple in a .user.js and very clean

There are a few reasons it is better to use a style-specific addon versus adding the style through a userscript

  • Even though you can run a userscript at document-start there may still be a FOUC. We've encountered this problem with our GitHub-Dark Script userscript, but we've never had a problem with our GitHub-Dark userstyle.
  • Stylesheets injected using GM_addStyle are appended to the <head> and even styles using an !important flag may be overridden by the default style if it also uses the flag.
  • Stylus manages this problem by immediately adding the style, then moving the style after the closing body tag once the document has completed loading.