Downvotes and upvotes work together to manage the visibility of posts that align with the community's tastes.
While I myself found an opportunity to reply to the GP and didn't down vote them, their comment only engaged with the article in a shallow way and only then, seemingly, to just dismiss the concept of solver altogether.
It wasn't a offensive comment, but it didn't really contribute to the site in the way many people digging into deep technical walkthroughs like this expect to see.
Some downvotes weren't guaranteed, but they're not surprising and they're probably helping new readers stay engaged with more topical and technical alternatives.
It's not the end of the world to get a few downvotes, and it's almost never personal. It certainly isn't here.
Aside: Downvotes on HN can be an expression of age related, self-righteous sniper pique; Opinions on what contributes to a conversation can be all over the place and are entirely subject to biases, which can be interesting (I guess). Doesn't really matter, and Hail Satan anyway. Also "Q for Mortals" is an interesting book.