You don't need
> no cookie popups, no "subscribe to our newsletter" slide-ins, no phenomenon where the content loads but then a second later the page resets and re-loads the content again (probably with more ads or something)
to fix rendering layout using tables and cell width to render comment levels.
Just a few lines of CSS and Arc really. That would be a big overhaul only because HN is very small, but not that big in absolute.