I generally agree, but what a few lines of CSS would make it much more pleasant to read IMO:

- limit container width so lines don't get too long

- larger text and more line height

And not really CSS but:

- Making it easier to collapse comments on mobile

I know some of those changes would potentially destroy the look & feel that some seem to enjoy around here. However on mobile currently it's only possible to enjoy HN via a third party app though.