I agree that the wording of the first statement is provocative. I don't think it's an insult, and I don't think that it's wrong. And honestly I don't believe that a provocative comment is necessarily a bad thing, provocation certainly has it's place in discussion.
And while "Americans should learn the rest of the world doesn't go around them" is provocative, in the americentric context of hackernews and essentially nowhere else, I fail to see how it a good faith interpretation of the post results in the conclusion that it was posted solely to provoke anger. It rather seems to me that it is provocative in order to force the reader to consider their personal biases.
While you would certainly be in your rights at Ycombinator to remove provocative speech, provocation made directly against the status quo or against the dominant zeitgeist or group in a forum is most certainly useful. Provocative comments such as these help remove pretense and veneer around arguments for and against dominant positions, and when they are made from the less dominant position they help remove the gravitas of more widely held or convenient ideas.
I'm not saying that this necessarily applies fully to the comment we are talking about, but stating the comment provocatively absolutely has it's uses. I also disagree that the intent of the comment was to provoke a nationalistic flame war, that depends wholly on the answers and the subsequent responses, and from what I've seen the answers to this comment are much more intellectually interesting that in the ~1 other thread, and I think if it was allowed to progress further would have been more interesting still.
This is because it's the only top level comment that addresses the implicit subtext of the purpose of the project. There is massive anglo- and frankly americano-centrism in the tech community. Anyone who makes any decisions in tech communities acts or is expected to act inside of the context of English, American culture, and so on. This leads to, in my experience, a lot of programmers and other people in tech who's working culture is American culture and whose working language is the English language to inform the landscape of tech. This is almost never addressed, except for cursory comments that are almost always inconsequential.
The very fact that tech culture is so overwhelmingly americano-centric and that almost nothing is ever done, or that it is almost never addressed when relevant, is why I think that provocativeness when addressing the situation can certainly be warranted. In fact, this is the main function of provocativeness in discourse, because it forces the dominant narrative to be questioned. I believe this to be in the good faith of allowing the discussion to go forwards. It is true that the spirit of the website is to be curious, and if the community did act in that spirit unavailingly all of the time equitably, provocation would not be useful. But this is not the case, neither will it ever be the case when the subject isn't objective tech, but instead deeply rooted almost unconscious assumptions about the world that frankly this community is not generally known for addressing well, direct provocation is, to me warranted.
If you take the example of this project for example, the entirety of the project is an exercise in Americentrism. Literally all of it uses the "default" American cultural point of view in order to make prescriptive recommendation about what is culturally better or worse for an international community. And yet, this is not even mentioned in FAQ, nor in any other top level comment. You won't find anyone questioning this, and indeed you will certainly find throughout the website countless examples of people celebrating the Americentric nature of discourse in technology.
It is not secret that Americans, in general, are more egregious in their Americentrism than other cultural groups are about their own relative ethnocentrism. This is sentence is, I believe in good faith, true. The only reason I can think of why one would find this less egregious than the leading sentence in the top level comment is because the interpreter would feel targeted by the former, or because one would be provoked. If someone is indeed provoked by that sentence, then I believe it is not a bad outcome - it forces the interpreter to be exposed to this very unpopular yet valid objection. In fact, strong and provocative language in these subjects may be much more effective in driving out interesting discussion than milquetoast, matter-of-fact discussion, which is much better suited to other subjects. Being provocative, even arguing for a position more extreme than your own, is important and when exploring an underexplored yet important subject can honestly be better than disaffected disconnected discourse for all parties. If one cannot answer in good faith to a provocative or attacking statement, then something is lost. Passion in discussion especially in such a profound subject that is difficult to understand because of cultural factors is not a bad thing.
The dialectic between thesis and antithesis is very enriching when talking about non-material subjects. It shouldn't be eschewed simply because the opposition may attack the person indirectly, that is unavoidable in such discussions. Putting up more of a veneer is generally unhelpful.