I don't personally have a problem with Mozilla trying to defend the open web. If anything should be their mission, that's a good one.

And while XUL is the base that many extensions have been built on, Mozilla are quite right to throw it out. If Firefox chucks it, I doubt forks of it will manage to maintain it well. It's half-dead already.

Killing XUL is not a problem in itself, what's not clear is whether WebExtensions will support the same advanced features, and the goal of keeping compatibility with Chrome implies it won't.

Chrome compatibility isn't a major goal, IIRC. WebExtensions are based on the Chrome API but will neither necessarily implement all Chrome features, nor be restricted to the set implemented by Chrome, AIUI.

Well, it sounded like a major goal in their announcing blog post:

We would like add-on development to be more like Web development: the same code should run in multiple browsers according to behavior set by standards, with comprehensive documentation available from multiple vendors. To this end, we are implementing a new, Blink-compatible API in Firefox called WebExtensions. Extension code written for Chrome, Opera, or, possibly in the future, Microsoft Edge will run in Firefox with few changes as a WebExtension.

https://blog.mozilla.org/addons/2015/08/21/the-future-of-dev...

Killing XUL is actually a significant issue. It affects:

-Thunderbird

-Instantbird

-Nightingale

-Celtx

-Blue Griffon

-Pencil project

-Komodo IDE

And others.

Fair enough, I meant to Firefox itself.

Considering that Pale Moon strips out accessibility in the first place, I'm not sure an extension designed to increase keyboard accessibility would be the best fit.

Frankly I am pondering going back to Seamonkey (what used to be the Netscape/Mozilla application suite).

SeaMonkey likely has even fewer resources to maintain the mail engine within than Thunderbird does.

I use Seamonkey as my newsreader, works pretty well.