To be pedantic the ad hominem fallacy is about trying to deny an argument by attacking the author, so in a discussion about zig Vs rust if Andrew isn't trying to enter the discussion and just argue "that guy was stinky, glad he is gone" is not really an ad hominem, just not classy let's say.
> if Andrew isn't trying to enter the discussion
But he is. Both in the title, and in later half of the blog post, he directly enters that discussion. I'm not saying an ad hominem argument is always bad, but this clearly is one.
You're both right: the essay does not really contain ad hominem fallacies, but the essay itself is surely an ad hominem attack, on Jarred as a person. No judgment here, I don't know Jarred or Andrew at all, but like other commenters I did find the closing paragraphs saying the author has no ill-will towards Jarred quite unbelievable.