However, to be fair, these seem like themes. And themes are wonky voodoo magic, and aside from requiring a lot of effort, nobody gives a damn about your work. I’d say themes and other aesthetic extensions get abandoned far more often than extensions that add functionality.

Also Classic Compact is the best theme forever.

Aside from that, it’s pretty easy to force Firefox to accept add-ons that you know are working. Slight problem: if you update and an extension really doesn’t work, you’ll be sad. Anyway, I think this extension is the current solution. Alternatively, Is It Compatible? will let you know when to wait to upgrade Firefox.

PS: I can’t help being a Mozilla apologist, okay! In principle, though, I like that you can dig around in the guts of Firefox beyond anything that Chrome’s API supports. On the other hand, I can’t help but be envious of a lot of Chrome extensions that have no Firefox equivalent because they’re so much easier to make. All of which is to say that I realize I am a flawed human with illogical software preferences!

PPS: If you have to restart Firefox to use an extension/apply a theme, it’s because it uses an older API for Firefox. Which, I believe, uses an ugly mix of C++ and JavaScript. “Restartless” extensions use a newer JavaScript API, which is still a work in progress by my understanding. It’s more in line with what Chrome offers, but I don’t know if you sacrifice anything by leaving behind the double-edged sword that is C++.