This is written by the same guy who wrote Helpful, an enhancement package for the Emacs Help buffer. I highly recommend checking out Helpful if you haven’t seen it. https://github.com/Wilfred/helpful

Not to discredit Wilfred (it looks like he's taken over the project as the maintainer), but, based on the historical contributions [1], it looks like it was originally developed by Max Brunsfeld, who also created Tree-sitter. [2]

[1]: https://github.com/Wilfred/difftastic/graphs/contributors

[2]: https://github.com/tree-sitter/tree-sitter

[3]: https://github.com/Wilfred/difftastic/commit/958033924a2dea7...