Writing using authoritative language is very common, and widely considered a best practice.

I highly recommend you simply accept it as what it is: the way some people communicate, especially online. It's not worth your time/attention/care to think about this.

I was just thinking that, I hate article titles that are phrased exactly as a command and it's merely a blog post that wants to change an entire body of thought that's well founded.

I take all direct orders as suggestions. Sometimes this gets me into trouble; The same way it does my 2 year old. Most of the time though, it's the way to go.

No, I got quite mad when I read the whole promotional article for his new node.js program without seeing a single argument against REST APIs.

Would it help if he prefixed it with "In this article, I argue for why I believe that you should"?

I was thinking about this yesterday, but its seems like HN likes that kinda thing. Lots of frontpage article are direct orders from blogs with who knows what credibility.

You aren't, but it's a mistaken thing to dislike: there's no value to rephrasing it as "I believe you should [do X]" or "I am arguing that you should [do X]" because that's necessarily always true anyway, i.e. no article can ever be anything other than what the author believes and argues for. So 'softening' the language would be inefficient - it would use more words while adding nothing of substance.

I read it as (I'd like to show you something that may help you) "Stop writing REST API clients". Imagine trying to visually scan HN article titles having to filter through useless pleasantries like that.

It irritates me too.

Try reading that with the voice of Morgan Freeman. Now THAT is something you would likely do :)