It's so much better than any of the extension-based XUL interface hacks. As soon as they can figure out when to auto-expand the sidebar it will be perfect.
Yes, because the APIs aren't perfectly fleshed-out. And they may never be, and yet that's still completely OK because the WebExtension model is obviously better along the performance, security, portability, and API stability axes.
This is blatantly false, and one of the most dishonest and manipulative claims that I've seen on HN.
Performance is performance. If one technology is more performant by removing features, useful or not, it it factually faster, and that performance absolutely does count. Features are completely irrelevant to performance measurements of a system.
If you have two cars, car A with top speed 160 MPH and a 0-60 of 3s, and car be with top speech 120 MPH and a 0-60 of 5s, some people may still prefer car B because it has better mileage or nicer features or is cheaper (which is the overall value judgement that you seem to be extremely confused about), but precisely zero sane people will tell you that car A "isn't clearly better from a speed standpoint" because it has less features than car B.
Crippling my ad blocker doesn't make my browser faster on average, even though dishonest benchmarks from advertising companies may claim otherwise. Removing XUL also didn't make TreeStyleTab faster; quite the opposite.
Aside from crippling ad blockers, are there any other theoretical performance improvements enabled by WebExtensions, or is it all about reducing opportunities for badly-written extensions to have an impact?