I think they mean the tendency to take a statement and apply maths or logic to show that it is incorrect (or less frequently, correct).
I regularly do this (to the frustration of those around me) and I think there is a strong correlation between enjoying hacker news and having this personality trait.
No, the point is not simply using math to show something is wrong. It's using math to show something that doesn't need to be 100% correct to convey the desired meaning is wrong. It's pedantry to the point of wondering if the person responding has ever actually had a conversation with a human being that didn't involve a keyboard. If someone hears an elephant/mosquito metaphor in this context and starts doing math instead of simply taking it for what it is - a hyperbolic way of saying "this thing is really, really big/impressive/well-funded/whatever, and this other thing is... the opposite," that's a level of social awkwardness and borderline autism that is simply unnecessary in any discussion.
Okay, DDG is a hyena and not a mosquito. Great. Tell me how that changes the meaning of the article, or the strength of the facts used, or its conclusions, or the credibility of the author.
I regularly do this (to the frustration of those around me) and I think there is a strong correlation between enjoying hacker news and having this personality trait.