In what way? I find this website perfectly readable, and the font size and line height were appropriate enough.
There's a JS-based fade-in on page load (or at least there was; the author mentioned that it'd be changed at some point) that doesn't bother to have a fallback. And as such there's a CSS rule that sets the post opacity to zero (making it unreadable).
There are many many many websites that don't work without JS that work if you disable both JS and CSS. This being one of them.
That being said, even other than that there are a number of things I don't like about the website. All personal preference, however. (Namely: 85-85-85 font on 255-255-255 background isn't the best, contrast-wise (I have a laptop and am often outside - readability trumps fashion for me); I don't like the trend of narrower and narrower line widths (It looks bad enough on my laptop, on a 2k screen 700px width would just look ridiculous); Ditto, I don't like the trend of higher and higher line heights - 1.2 is plenty, 1.5 is overkill, this site is 1.7; Continuing on the trend of "why do you put so little on the screen", I find the paragraph separation also overkill (1 line between paragraphs or equivalent is fine, and maybe two between sections)))
The line length (measure) on that page is about 60 ems. This is much longer than the optimal value for readability, which is 30 - 40 ems.
> Ditto, I don't like the trend of higher and higher line heights - 1.2 is plenty, 1.5 is overkill, this site is 1.7;
As the measure increases, leading (line height) must also increase for legibility, because it's harder to track longer lines with the eye when 'returning' to the start of the next line.
A leading of 1.7 ems doesn't seem unreasonable to me for such a long measure.
For me, type on the web is a lot better than it used to be: tiny type on ridiculously long lines. There are some holdouts though; Hacker News for example.
I just wish that HTML had a sane way to allow client-side preferences (Like, say, line height and width) to be expressed.