Yeah, but so what? It is, nevertheless, recognizable to nearly everyone. In a world where cars still advertise their "horsepower" and pencils have graphite compound "leads" we can probably live with an icon that is well understood but whose original referent is no longer familiar.
This isn't an argument against vestigial iconography. It's not even an argument against skeuomorphism. It's a recognition that skeuomorphism increasingly fails to serve its intended purpose of conveying a meaning. Once we recognize that the old icons are dead metaphors, that we often times keep them only because of inertia and not because they have any intrinsic value, we can build momentum on the necessary work of establishing the visual language of the digital age on its own terms.
Language is full of dead metaphor. Words and symbols have meaning because they have been given meaning; most of the associations might as well be arbitrary. Doesn't matter; humans are very good at recognizing these associations and deriving the intent.
As for the rest of your comment, I'm not sure what you think I was trying to make sound difficult. I was arguing that it's entirely possible to replace the floppy disk with an arbitrary symbol, and it's just inertia (user training and a strange sacredness afforded this one random icon) that really keeps it around. I think assosciating a distinct symbol with an action is pretty damned easy, actually. (Designing a good symbol can be hard, though.)
Of course it's possible to pick a different symbol to represent the action of saving data to permanent storage: but why bother? We have a symbol, and it's as good as any other arbitrary symbol might be. Changing it would create confusion for no benefit, since it's ultimately the association of the symbol with the action that matters, and not the history of that symbol's origin.
The younger ones don't seem to know what one is, but the older ones do.
If stop signs showed the picture of the brake lever from a Ford Model T, you'd have a point.
I agree that the octagon is arbitrary. But that's beside the point, because it's self-evidently arbitrary. Nobody assumes there must be a deeper meaning behind a basic shape. The iconography of a floppy disk is not a basic shape.
I guess I don't see the point; you'll just confuse people who already know what the old icon means. Our letters aren't particularly brilliantly chosen (arguably other systems are more logical or easier to learn), and yet who wants to replace them?
Importantly, the user has no reason to directly contrast the new icon to the old one. The user doesn't answer the question "Is this icon as effective as that old one?", they simply have to answer the question "Do I know how to perform the action I want to perform?", and as long as your save icon clearly communicates its meaning, there shouldn't be much/any confusion when the user tries to save. They'll look for something that seems to say "Click me to save", they'll see your icon, they'll say "Hey, that looks like it means 'Save'!", and they'll try it. (Aside: I don't say this randomly, I'm speaking from experience here; there have been plenty of applications in recent years that have tried out new "Save" icons, and I can't say I've ever had a problem figuring out how to save with any of them.)
As far as what "the point" is in changing out the icon, the point is that the entire reason for using action icons on buttons, etc. is to give the user an intuitive sense of what action will be performed when they click it, and as time goes on, the link between the floppy disk and digital storage will become weaker and weaker. And while it may be true that we could drag that symbol with us by convention, my question would be, why bother? If we can come up with something better, especially if we can find something that isn't tied to any specific technology (and I'd argue that we have), isn't this an improvement? I can't think of any advantage the old icon has over new ones other than the small advantage that it's familiar, but, as I said above, I don't think that's enough.
In other words, instead of asking "Why should we get rid of the floppy disk icon?", I honestly think the better question is, "Why not get rid of the floppy disc icon?"
So in summary, while I agree that it's sometimes fine to use an old icon if enough people understand what it means by convention, this is not a good reason to avoid using the newer, less skeuomorphic icons that the linked blog post was trying to argue against.
You point out that while the quill pen was long outdated when it was first used, "everyone still recognized the contents of that icon", but that's exactly the problem that the GP and GGP are pointing out: more and more of the old skeuomorphic icons reference real world icons that younger users (and indeed some older users) actually don't recognize. Notepads, sure, we've still got those; contact books, eh, you'll see them once in a while, but tbh when I see a bare "contact book" icon without a label it occasionally takes me a second to figure out what I'm looking at; floppy disks, as has been argued to death, are entirely a thing of the past, with the exception of old systems and archives still in use in dusty university basements. Young users today essentially just know the image of a floppy disc as "the save button" without any skeuomorphic rationale backing it up.
The skeuomorphic link between computers and the physical objects we use is is constantly degrading, to the point that using skeuo icons can sometimes actually inhibit the user experience and slow the user down while they try to figure out what they're looking at. We have common patterns emerging with no or very little connection to the real world; a great example would the "hamburger" menu button. If there's any metaphor there in the user's mind, it's to the row items that will appear when you click on it, not to anything physical, yet it's perfectly comprehensible to anyone who's been using digital devices for any length of time.