In this case, I think the generous interpretation is that the poster simply missed that section of the article. The generous interpretation basically requires one to conclude he read it, because otherwise he wouldn't make the connection to deprecation from the title alone.

The article in question is usually not the topic of conversation on HN. It is better to consider it to be the launching point for the conversation. Some will discuss the article, certainly, but you can expect the conversation to branch out very quickly to related items (especially if those items are mentioned in the article). While it's probably not a good idea to discuss the plight of African elephants in these threads, drawing attention to a minor, but specific point in the article is perfectly cromulent.

In this case, the post has value. It does two things. First, it draws attention to a subtopic that was only an aside in the article. (One I happened to miss the first read-through.) Second, the phrasing in the article is somewhat general and vague about this, and the post is relatively more specific and direct.