I like questions that show how useful it is to have only one thing you're optimizing for. They're easy to answer and the answers are sometimes surprising.

On HN, the only thing we're optimizing for intellectual curiosity, so to the degree that a post gratifies intellectual interest, it's fine. If the 30 most interesting things on HN happened to be ads, then the best front page that day would be all ads. Of course that won't likely happen before the universe ends, but still, it follows!

The problem with content marketing is that it tends to be lame. If someone produces a genuinely interesting article in the genre of "we used our product to do X", that's not only ok, it's interesting in another way too: "we managed to make content marketing not be boring".

One thing that's not ok, of course, is for people to get others to upvote their content marketing in order to promote it. But that applies to every submission. And the votes on this story look clean.