Josh Seiden provides a good response to the argument that designers should avoid coding.  He also articulates some of the reasons why it is advantageous for digital designers to incorporate code into their workflow. 

(the) argument–that designers shouldn’t be coders–is based on a fundamental insight that I find compelling: if you are paying attention to how a software system will be built, you will be influenced by that need; if you don’t do something to counter that influence, you will end up with software designed around what Alan Cooper calls the “implementation model.”

We should be mature enough to throw out ideas that are unduly influenced by the system model.

The difference for me is that more good product comes from this workflow (desingers working with code). In my experience, having designers in control of the presentation layer results in a presentation that more closely conforms to the designer’s intent. I imagine that most designers would think that’s a good thing.

I firmly believe the deeper a designer understands their medium the better their designs can be.  Nobody would argue that a deeper understanding of paper, inks and the printing process enables better print designs.  The equivalent for UX and interaction design is understanding code and the specific technology platform you are designing for (web, iOS, Android, Mac, Windows, etc).  The key is to understand the platform without forgetting the user.  I'll have more to say on this topic in a future post.

Craig Dennis reminds designers that good design must always consider the full user experience, not just the happy path:

Empty states are places in apps that have no content or data. They are empty. A blank page. Traditionally empty states are overlooked as most designers focus on how best to display lots of content or data. It’s common for empty states to be dealt with by developers as they are often caused by exceptions (such as no internet connection). They often write the copy and as a result it can be a little difficult to understand or it is left with the basic styles. Not the best combination. It should be logged as something that needs designing but that doesn’t always happen.

While Craig focuses on empty states in this article there are many other edge cases to consider.  It is a good idea to go make edge case analysis a part of your regular design process.  It's also a good idea to request that developers discuss any new edge cases you hadn't considered with you.  Every aspect of the user experience should be designed with intention.