It's a wonderful quote, because it also says that before coding you might want to learn cognitive psychology, social psychology, gestalt theory, marketing, copywriting, information architecture, usability, economy, statistics, science of materials, architecture and so on and on. :)
There's not just "design" and "code" out there, the design field is way more deep than that, so that quote might translate well to a designer that can't code, but studied in depth social psychology, urban architecture and team cooperation techniques. :)
Please, try to understand that there are different kinds of people, intelligences, sensibilities and talents, and that what's easy and simple for someone, might be hell for someone else.
Some professionals might do a more than excellent job if they focus and pair with a developer, instead of trying to be something they are not. ;)
Some others instead, might become better professionals by learning how to code. Different people, different skills, and they can both work on the web very efficiently in both small and big teams. :)
I love the attitude you express in the third paragraph. We need way more people willing to teach and support others understanding them. :)
What it tries to clarify - and well, it might have failed, of course - is that we should stop to simplify the problem as "designers should code", because not all designers should. But yes, all designers could, and if you feel that way, or you are prepared for that, or if you want that, you can learn to code. Exactly like a developer can learn how to design.
In either case, exactly like it's wrong to say "developers should design" but it's correct to argue that a developer with design knowledge will be better at its job, it's equally wrong to say that "designers should code", but it's correct to argue that a web designer with developer knowledge will be better at its job. ;)
I think the difference is that the author defines "designer" as someone who excels in some "designer-like" quadrant of the intelligences. Which is a load of self-entitled bs.
A designer is someone who designs—it's defined by action, not beliefs about competency. If you design things implemented in HTML/CSS and you don't have any proficiency at all in those technologies then you're very liable to be a worse designer than someone who does. The argument of how often that is true is what's important here and it's never actually discussed in the article.
Pigeon-holing? Quite the opposite. I'm making the difference between "should" and "could". That's exactly because not everyone is a specialist, neither I am, but at the same time not everyone is a generalist! :)
Exactly like I'm saying in the middle of the article, "you have to know this stuff", but you don't have to know also how this stuff is done, you can, of course. But it's not a must. :)
It's always sad for me to hear people with bad experiences with designers or developers, but really, I don't think that "code" is the answer. I believe that "teamwork" is the answer. Knowing. Discussing. Collaborating. I've never seen a team doing that failing, regardless of the mix of skills :)
It's the "Theory of Multiple Intelligences" bit that gave me the impression of pigeon-holing. And the paragraph preceding it where you go on about the typical high-school stereotypes. And the rest of the article is built on the premise of a dichotomy where creativity is separate from technical ability... the whole "left brain/right brain" idea.
I think the split is actually in designer/front-end developer.
If you want to make analogies to other industries, I think your concept of designer is more analogous to a "concept artist". The person who has the good ideas that are not restrained by the burden of having to think about how to build them.
And I think for most projects the designer is also the concept artist. Very few (if any) web projects actually need those roles filled by two separate specialists.
So I don't think it's bullshit. Designers should know how to code. And they should be good at it too.
Again, I agree. The whole article isn't built on that dichotomy. It's just a sequence from a simple perspective to a more complex perspective, and actually ends saying that it's better if you are willing to expand your view, exactly like you are saying. :)
On the second part of your comment, well, you are talking about "web designer" specifically, and with a very specific definition of it as well. If that's your definition, then yes, he have to do that. But er, it looks more like a Frontend Developer to me, and I never heard of a "Concept Artist". ;)
However, it's a matter of terminology here, and there's surely some confusion about it. :)