Needs to be integrated into Thunerbird Rated 1 out of 5 stars
It's time this add-on became part of the Thunderbird source code.
It's dumb to have it as an add-on.
Of all the dumb things that have been added to Thunderbird, this is one thing that would be smart.
I understand your concerns, but please do take a moment to think about the backside. If Lightning is part of Thunderbird, it will need more people working on the project regularly, since its much more critical that changes don't cause regressions.
* We would need more/better unit tests and automated UI tests.
* There are still numerous issues with performance that need to be fixed
* There must be more people working on QA and Support, since complaints on Lightning will then be processed by the Thunderbird team
* There must be more bugzilla triagers that move bugs into the right components.
and maybe some other issues. Its just not that easy, especially with the current amount of community contributions.