Correction, in my previous reply I meant to say that the Safari version of Stylish (not stylus) has a different developer and doesn’t appear to share the Chrome/Firefox extension’s tracking issues.
With a quick glance it looks to include google analytics, but that’s only used on the extension’s settings page and doesn’t send browser history or anything like that. JS isn’t my forte, though, so if anybody else could take a look and confirm that’d be great.
If you do write such an addon as you said, please advertise it here in HN!