I don't really want to disagree with you in public, but in this instance I really think I have to. In your latest blog post you equate "community" to "everything open-source" and I don't think that makes sense. Is there a "Microsoft Community?". Sure, there is. There are active user groups with tens of thousands of members across the world focusing on all kind of aspects around Microsoft products that exist in independence or under the umbrella of INETA, Culminis or Mindshare. There are fantastic developer community sites out there like CodeProject, DotNetJunkies or ASPAlliance, we have a whole network of Microsoft-driven community sites with a lot of community engagement in forums and community samples (ASP.NET, IIS.NET, etc.) and CodePlex is actually quite impressive for hosting open source projects. The code for this blog engine is on SourceForge along with hundreds and hundreds of Win32 and .NET based other projects.
It goes further. How about JorDev in Jordan? How about Developers.ie in Ireland? CodeZone.de in Germany? NNUG in Norway? SDN in The Netherlands? GotDotNet.RU in Russia? I could continue this list for several pages. And a lot of these groups speak and publish in their local language so their activities don't pop-up on the New York, Redmond, or Silicon Valley radar screens. In the last 4 years before joining the firm I've spoken at some 250 events in over 40 countries and I can tell you, the community you say is missing is there and very much alive. We even seem to have rabid fanboys like Apple, if someone were to believe this unbiased complaint ;-)
But to the heart of your story. You write "When the vendor whose technology you are using doesn't require your participation to create/advance its products, you tend to feel less personally vested in that vendor." The reality looks different. We require that participation and that participation happens. In fact, customer-defined requirements and quality gates are part of our release criteria these days. We broadly engage in technical discussions in blogs, we invite and solicit opinion from industry luminaries, we listen very closely to what people have to say in the forums (and file bugs and design change requests as the result of it), we speak to customers on on-site visits, we run small and big Software Design Reviews previewing and discussing very early bits or just raw ideas (my division ran such an event right after MIX on the 1st floor of the Venetian Convention Center), and there's a a lot of email (and IM discussions) going back and forth with individuals on a daily basis that helps us doing the right thing. And we're not shy changing plans if we're being told that we're not doing the right thing.
The only thing that we don't do is allowing everyone coming along to check out files from our source code depot and start coding along. If people really want to do work on the internals of the .NET Framework, we'll figure out their skills (as even open source projects eventually end up doing as they succeed and grow), see what parts of the code they can best work on for design, code or test, and hire them if it's a fit.
Lastly, to your question "Could/should Microsoft try to make Visual Studio running on Windows more appealing to Linux developers and deployers? Port Microsoft Office or SQL Server to Linux?". Should we? Not mine to decide. This point isn't about "community", at all, I believe. There's a huge, world-wide community that focuses on Windows and the .NET Framework. A significant part of the open source community build software that runs on Windows - and in very many instances even exclusively on Windows. Isn't that the community we should care about in the first place?
As much as folks with vested interest want to play the story that way, the open source community isn't all about Linux (let alone Java). I don't think anyone at Microsoft needs to have "Slashdot envy" as Scoble once put it. Our community does fantastic work and does a lot of it. It'd be nice if you'd recognize them for it.
And you write "Even though Microsoft and its products have helped a number of resellers, software vendors, peripheral makers, consultants and programmers carve out a living for themselves, most of these folks seem to consider Microsoft a job, not an adventure." The adventure made me move from Germany to Redmond and work for the firm. The adventure has made me lots of friends all across the world. I love this stuff. So do my friends. It'd be nice if you'd recognize that as well.
Have a great day!
PS: I'm not cross-posting this to the MSDN blog as I usually do these days. This is my personal opinion and one motivated by me feeling to be very much a member of the community that you say doesn't exist.