The top Reddit response cites some good reasons why this may be so. The writer mentions they needed to move from Node to improve "throughput" (and .NET was suggested). In what way would .NET improve performance that Node can't satisfy. (Isn't Node's worker thread sufficiently close to ASP.NET, ISAPI multi-threaded scenarios?)
In my opinion, you can go a bit more low level in C# and have control over allocations, data copying, threads, etc. Also, .NET is a bit more general purpose than Node. If the workload is more about computation (CPU/GPU intensive stuff) or has some unusual technical requirements (uncommon protocols, interop, etc.), you can really benefit from being lower level and more generic.
But all this is very project specific... it's hard to make these sort of claims about performance.
The top Reddit response cites some good reasons why this may be so. The writer mentions they needed to move from Node to improve "throughput" (and .NET was suggested). In what way would .NET improve performance that Node can't satisfy. (Isn't Node's worker thread sufficiently close to ASP.NET, ISAPI multi-threaded scenarios?)