Firefox uglification

The Internet is having a bad few days. One of the many recent security issues is a compromised certificate authority that -- get this -- used "4" as one of its keys. Some browsers including Firefox have applied mitigations, so I updated Firefox. It came back pink and full of rounded corners and visual crap. That was unexpected. I was able to fix the pink sprawl by installing a theme in the appearance settings, but even though the preview image showed square tabs, they were still oval. An oval has less usable space than a rectangle with the same height and width and for tabs that signal is the tab's identity -- Do Not Want. I haven't been following Mozilla development stuff, but apparently there is some new UI framework or some such called "Nova" that, according to messages in this Mozilla support thread, is quite intentional and is going to be forced at some point. I don't know what Nova is and what other changes it's going to bring, but at least for now, you can turn it off by going…