I do have quite a bit of programming experience (close to 10 years by now, C, C++, etc. and everything that goes along with it) and to be honest, the author of this topic is partly right. The code in K3D is more extensible and it's a joy to use compared to the code in Blender.
There's even a way to write your own graphical interface for it, without the need to rewrite the rest of the program as well. I have once tried to do that for Blender.. well, trust me.. everything (data structures, screens, spaces) is so closely connected that it's nearly impossible to use something else for the gui. It would basically mean that you would have to write a complete new application from the ground up, which could use some of Blender's libraries, but that's not really worth it because the largest part of Blender's code is in the interface. The rest could mostly be replaced with alternatives (if you're using C++ that would be easy as pi, with ready to use libraries like the STL, Boost and so on).
I know this because I tried to make a comparable interface using Qt. I did succeed at integrating the spaces within OpenGL views from Qt, and I also succeeded in taking down the whole multi-window management of Blender, but hell.. you really don't want to take it even further than that. Ripping down all hardcoded shortcuts was really hell and is still not finished. It won't get finished either because it's quite a job to keep things in line and stubbed nicely with the latest svn version of Blender (as ton already noted at the sunday meeting for his own tool-refactor).
K3D on the other hand, makes it far more easy to do something like that. You can plug in any gui toolkit. Altough it sounds more simple than it really is in practice, it does prove how the code of Blender is less extensible in one of many ways, and how K3D's code is much more future proof.
I've got experience with that as well. It took me two days to get a very basic K3D interface using Qt up and running, compared to the two months it took for Blender, with less functionality.
Having that said though, the authors of K3D definitely know how to build great code that holds up in the future, but they don't seem to know very well how to build a usable interface around that great code. In that respect, Blender is more future proof.
Oh, how much would I dream about K3D with the interface and a number of other inner workings from Blender... that would be close to nirvana, I guess.
