I can give you the honest accounting of my thought process, since it seems to be of interest to you:
I read your root comment about McCarthy being wrong about repeating words in academic writing. I thought to myself, "this is exactly the sort of dismissal we tend to traffic in here, the assumption that we're subject matter experts on research and STEM and that a writer wouldn't be". I figured a bunch of people on HN would be instantly persuaded by the fact that your comment attests to experience in academic writing, especially since so few of them will closely read the article itself, which notes McCarthy's unexpectedly deep experience with hard science academic writing.
Then I thought to myself, "you know what? Cormac McCarthy is pretty universally considered one of the greatest writers of the last 50 years, so it is probably pretty safe to suggest that his writing advice not be dismissed easily, even by someone with their own deep experience with academic writing". That is to say: it's no great put-down to suggest that someone's own writing experience might be subordinate to that of... Cormac freaking McCarthy. :)
There's nothing especially interesting about "taking down authorities" on HN --- it's the air we breathe here. I do it too, all the time. By the same token: pushing back on that instinct seems totally within the bounds of our discussions as well.
So, long story short: I thought your comment was a bit facile and dismissive, and said why (or: almost did, but deleted my comment when I saw 'brudgers better one, then cosigned theirs).
Hope that helps.