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.
But I do acknowledge that's a relatively recent change (last few years).
To me, it seems like a win for everyone.
- I hear about the company while learning something interesting. I'll probably remember their brand.
- The company has people actively searching for and promoting their article (e.g. on HN) instead of trying to bypass or block it with adblockers etc. And this article might bring in leads and sales for them years in future, instead of only while they keep throwing money into adspend.
- A writer who is interested in technology and writing gets paid, instead of that money going to Google / some ad agency who randomly puts levers on and off hoping to make the conversion rate go up.
- An editor, designer, proofreader, technical checker etc etc all get involved (as opposed to a one-person blog piece with a similar goal of "look at this cool thing I made") -- also people I would like to see supported more over ad agencies.
I think (hope) that "marketing as education" -- e.g. actually high quality content that also promotes a specific brand instead of the cheap "content marketing" that so many people are trying now -- will be the future of marketing once people realise they don't want to be tracked so invasively, adblockers get better, laws tighten, etc.
Anyone talking about what they do is an 'advertisement.' I don't know what good marking them would do - you should be as skeptical about anything anyone tells you whether it's an advert or not.