The are startups using it. We're just not in the MS bashing bandwagon you see here on hn.
I've not seen any thread on HN bashing MS without reason. However, the only guys who claim to use C# either work with big companies or freelance.
Some context has shifted, the Microsoft takes over Github part has shown sentiment shift also ( not everyone of course)
Beyond that, MS does deserve the skepticism it gets, and I'm not a fan of the "M$" references or similar. Leadership at MS has changed and it does show. I do wish they'd stop doing sleazy things with windows though. I've been using more Linux and Mac as a result.