I think it's more people who don't read the article, pattern match on a keyword in the title, and go off on a tangent on that keyword.

Article comments should be relevant to the article posted, not any unrelated topic that simply mentions the word.

Well yes, I think that's how the tangents get started. If the article itself is sufficiently interesting or the tangent is particularly off-topic, those conversations get quashed pretty quickly. There were only a couple top-level comments about the mixers, it just happened that there weren't many comments about the article itself to counter-balance them.