One of the nice things about a site like this is being exposed to domains that one is not familiar with. I for one know beans about physics simulations like this, so it is interesting.
Also, as someone who recalls what Javascript was like 10 or more years ago, yes, I am impressed with what it can do now.
I suppose this is true, though the same could have been said for flash before Javascript's recent strides, and I don't recall anyone being particularly excited about similar demos implemented in actionscript.
1) HN wasn't that big (or existing) at that time.
2) Now you can also see the code, it's not in some opaque swt archive.
3) You don't need a proprietary Adobe IDE to code it (yes, you could do without for Flash too with some bizarro third party tools. Talking about the mainstream).
4) Everybody hates flash anyway.
Of course experts are not impressed by things they are familiar with. But usually experts are pleased that something has bought interest to people not familiar that domain. For example, people are still blown away by the sight of a far away galaxy in a telescope. Astronomers love this, they don't suggest such wonder is "odd" because they are used to it.
But you missed the more important point in my post: if this wasn't in a browser, I'd never see it.
OTOH, realize that many readers here were probably not programming then.
Programming is the archetypal field where everything old is new again. The antidote -- dig up all those 1-2 day projects you did 10 years ago that you think are stupid / too simple, and re-package them for the kids.
I remember a good few years ago a colleague writing a fully textured 3D cloth sim that would remotely unfurl on your screen, displaying a given message on the cloth. He used it to display goatse.cx to me, which I wasn't very pleased about. This was developed in python and took him a few hours over a weekend as far as I remember, which seems about right.