> With http/2 the benefit of merging into one resource should be negligible anyways.
That's not true, by including them in the HTML you save an extra round trip for requesting them. That's what HTTP2 Push was supposed to solve, but it's being deprecated & removed.
> HN could put the CSS and JS into the generated HTML file and still stay under 14kB
At the expense of caching those resources that stay static. With http/2 the benefit of merging into one resource should be negligible anyways.