I've developed against Microsoft platforms for many years. I now, in fact, work at Microsoft. I do a lot of deep integration work with Visual Studio and I can tell you that it would be completely impossible without source code access. After working for a few months with source access to all of developer division, xbox, etc., that I never, ever, ever want to develop against a closed platform ever again. Most of our big partners who write VS add-ins do have source code access as well. You basically need it.
That is a completely separate task from learning to develop software.
You need platform source code access if you're doing low-level integration work, which is precisely what you don't do as a beginner.
Windows isn't the best platform for writing software but it's just fine. Python and Emacs work on it just fine, as do MySQL and other important software. Categorically asserting you can't learn how to structure code without having access to terabytes of C code is total fucking bullshit which is why I stand by the original statement.
I agree that is an invalid categorical assertion. To make it explicit: I learned to program (quite well, I hope) on top of closed platforms. However, I suspect that I would have learned faster, better, and more completely by working with open source platforms. My perspective on code has changed dramatically since I've embraced reading other people's code.
As an aside: although my integration work is "low-level", I do not get the opportunity to make changes or additions to the shipping VS bits. I can only file bugs and plead my case. I can't call secret APIs, nor do I gain any special powers other than the weight an @microsoft.com email address carries. I'm developing against the closed platform as all our partners, and non-partner customers.
