As there's a theme in comments here - I'm surprised people are so confused by the landing page. Between "a linter for prose" and the screenshot at the top of the page, I found it quite clear what the use case and point of the tool was. Personally interested where the confusion is- maybe unfamiliarity with "linting" or "prose"?
There is no clear explanation of what it actually is, just a vague sentence saying "brings your editorial style guide to life" which can mean a lot of things. And the screenshot is a wall of text in the smallest font size across the entire page (even smaller than the labels of the logos that make up 50% of the area), so if it was intended as carrier of important information it wasn't the right choice.
The HN post title says more in four words than the entire landing page.