it wouldn't surprise me if the .NET framework is an epicly gigantic codebase that no one person could be reasonably expected to read and review, like 100's of thousands of LOC.
So there's not much point in saying "open source baby", the Game of Thrones books are open source and I'm still not going to read them. And more importantly, is the byte-code interpreter open source?
When you're dealing with a product from an organisation with such a bad reputation as that of Microsoft, the questions are endless, and the answers are likely to be unsatisfactory. I don't want to waste my time.
(not to mention, Microsoft are now openly collecting all user data from their Windows users, what's the point in developing privacy software for an OS that openly exploits user privacy, why even bother?)
.NET Core is not .NET Framework. The former is cross platform the latter is Windows only. Yes, they are both open source and yes, the Roslyn compiler is open source, too. In fact I managed to contribute to the .NET ecosystem once or twice in the past, too. Please don't make comments like this when you have no knowledge of the subject.
Regarding your ad hominems on Microsoft, I believe they are worthy topics to discuss, but falls outside the scope of this discussion.