Isn't this the point of upvoting though - if people find it interesting and new, they will upvote and stuff will be visible.

I also think HN does some sort of deduplication if something has been posted recently (to count as upvote instead of new submission), but not sure of the details.

It's also the point of commenting. I think they were hoping for a more specific explanation along the lines of "I'm interested in it because it has X, Y, Z implications" or "Oxy continues to be important because ____ and here's the best comprehensive intro to it."