Rated 4 out of 5 stars
There need to be options for how to change the text labels on private tabs. Perhaps even an option to use a special favicon.
REPLY: If I'm understanding you correctly, I'd just put them in anyways (change the userChrome.css yourself) and, if an extension messes it up, it messes it up. But I don't see why it wouldn't also mess up the blue underline.
Thanks for the workaround, anyways.
You can found some styles for userChrome.css/Stylish here:
(but currently I don't have style to change tab labels, only example for icon available)
It's very hard to implement customisable appearance in case of many tab-reletad extensions and themes (e.g. there is at least 4 built-in themes: for WIndows classic and Aero, for Linux and for Mac OS). Thats why only UserStyles available – some of them should be corrected for some themes.