The way I see it - Microsoft has a different goal in mind.
However, Stack Overflow has specific criteria about what questions are appropriate for the community and Microsoft Q&A will have a more open policy regarding this. More importantly, via Microsoft Q&A we can create unique experiences that allow us to provide the highest level of support for our customers. It is hard to get a full picture of the customer who is asking a question on Stack Overflow. But on Microsoft Q&A it will be possible to connect the asker to their actual product usage and support contract. This will enable new opportunities to offer the highest quality support.
In this response, I take away the following:
- Microsoft Q&A wishes to have a more loose policy about what questions get asked on the site.
- Microsoft is explicitly leaning on this product as a means of supporting their products. Stack Overflow is very much not suited for that.
- There's a lot of metadata that makes supporting Microsoft questions "noise" on Stack Overflow - namely, "actual product usage" and "support contract". Those aren't details Stack Overflow cares about since support isn't the goal.
Besides, this has existed in one incarnation or another for their own products anyway.
This isn't a threat to Stack Overflow in the slightest, but that's not to say that there aren't other groups out there who would seek to create their own platform. Those that wish to face a daunting uphill battle in trying to pool together the actual resources needed to make something similar to the scale and utility of Stack Overflow, and frankly the only entity that could scratch the surface today would be Microsoft.
Although to be blunt, if it were the case that Microsoft wanted to truly ape the Stack Exchange experience, they'd just buy it like they did GitHub...