This is interesting. I wouldn't have assumed Metalsmith would be so far ahead for JS static site generators. Honestly, I've used a number of these (Metalsmith, Harp, Hexo and Wintersmith) and not been overly fond of any of them. Still much prefer Jekyll or Hugo - even as dev who favors JS.
I understand your point regarding the natural language parser aspect. Though the core does appear to parse the text, the plugins do appear to use preset regular expressions to pull matches. At this point, it feels somewhat inflexible...which I discuss in the article.
I updated the post to reflect that knwl is not "new." The post was just intended to be a fun experiment.