Looks great. Does it have a different scripting language, or is it still VimL? What kind of plugin support does it have? Is it embeddable? Does it have a messaging API like Neovim? How well does it handle long text lines and long documents?
No scripting language, most of the heavy lifting done in plugin is through shell calls (asynchronously or not). Example here [1]. I personally think that it's kinda hard to grok to be honest.
Thanks to the client server architecture, it is possible to make an external UI[2].
There is no line wrapping currently. Don't know about long documents, but the editor in general is very efficient.
[1] https://github.com/mawww/kakoune/blob/master/rc/core/grep.ka...
[2] https://github.com/mawww/kakoune/blob/master/doc/json_ui.asc...