Again, this just has no relevance to the claims on offer. You can evaluate them for yourself without wondering what the author's motives are.
I have no idea if the site is as sketchy as people claim, because I've never even heard of it before. But even if it is, I still wouldn't think the comment form comes anywhere close to giving unambiguous information about the author's motives. There are so many highly plausible reasons for this that you'd have to be thoroughly unreasonable to assume that it's strong evidence for any particular reason.
Sometimes they are actually written well enough or are so misleading that you don't even notice these things. I went to this article looking for affirmation of my own opinion (I happen to agree with the headline) and thanks to confirmation bias did not notice the comment form, and might have even bookmarked it or sent it along. Thankfully someone saved me a future embarrassment by pointing out that it's worthless as evidence, which is a large part of why I read the HN comments...
However, this is completely irrelevant to the idea in the article and does not take any merit off of it whatsoever. If you cannot judge an idea for the idea itself, what chance do you have at learning anything from anything you read?
Apologies, but these sorts of observations/criticisms are fairly common on HN (I remember someone saying "they don't follow their own advice" about the Stanford web credibility guidelines), and I have to say I consider them pointless. Observing hypocrisy and pseudo-hypocrisy is necessary if you're making a decision that depends heavily on someone's character, like electing a president, but it's almost always irrelevant when assessing the merit of what someone says.
People often have good reasons for not implementing their own advice, too. Maybe it was a higher priority for them to get the word out rather than make sure everything public they do complies with it first. Sometimes it's a cost-benefit problem: improving blog comment forms probably won't make much of a difference to their bottom line, but improving a new user sign-up form very well could. Comment forms are also fairly standard in what information they expect and in what order, so again, probably not a huge payoff. In Stanford's case, they already have the credibility that comes with being Stanford. Etc.