Dan's representation of things is wildly misleading. We worked with him extensively and even had him over to a 4th of July party the year that he was working on Julia stuff. Dan wrote a fuzzer and found a lot of obscure but not practically important bugs, almost all of which were nevertheless fixed quickly. He also found a few other less obscure bugs which were also fixed, usually within a few hours. He made a number of fixes himself as well, for which we were and still are greatly appreciative.
Dan had complaints about various things about Julia at the time. He was in the habit of emailing me directly about them. This is not great form in open source, but we were personally acquainted so it was fine. However, since I didn't have the knowledge or time to fix most of these issues, I generally encouraged him to post them on julia-dev or GitHub. As I recall, he usually did not.
As this continued, I encouraged him to write a constructive blog post about what he thought could be done better. Instead, he wrote a gotcha piece—the one posted here yet again—that implied that we don't care about bugs or software quality and had ignored or dismissed issues that he'd reported. He had been studying what kind of content does well on HN and how to get on the front page [1], and it's tempting to speculate that he knew that a dramatic criticism would get much better traction than a fairer critique.
Shortly thereafter, in a semi-private forum which I was also on, he wrote a lot of significantly less kind things about about us. I responded to his semi-private "shit talking" in what I still think is a measured fashion. He did not appreciate the pushback and amended his formerly glowing review of the Julia community to what you now find in his blog post. I am the "core dev" that Dan is obliquely referring to. In retrospect, I guess I shouldn't have pushed back at all and just let it go. But having someone who you have gone out of your way to help and showed every hospitality and kindness to, then turn around and talk smack about you in a place where they know you'll read it, frankly really sucks.
Two of the people who look the worst are co-founders of Julia. Are they not involved with Julia anymore?