It barely works on non MS platforms,has had many slightly incompatible versions so it's a non starter for many projects where I run into that might benefit from c#. I spoke to a manager recently who had invested in silverlight in the past. Based on that alone it was a no MS policy for his development teams.
Quite a few languages "loved" by "Linux communities" tend to have rather rudimentary integration with Linux kernel's facilities or worse packaging story.
For example, Go does not understand cgroups limits and needs an external package to solve this. .NET can read and accommodate those natively. It also ships with excellent epoll-based socket engine implementation. It's on par with Go (although I'm not sure which one is better, but .NET performs really well on high-throughput workloads).
