It isn't entirely clear who should be listed in `AUTHORS`.
http://man7.org/linux/man-pages/man7/man-pages.7.html :
>                     lists authors of the documentation or program.
(along with a paragraph telling that this isn't the place to give an exhaustive list of all authors)

Fixed by @sebastinas in b40e4ccfff8aecf776593305597f7979e418ced0 (explicitely written who did what).