There is A LOT more. Microsoft has dedicated teams that contribute to the actual C++, Java, Python development. If you use those langs you use code and standards developed by the Microsoft employees.
VSCode: https://github.com/microsoft/vscode JDK: https://github.com/microsoft/openjdk TS: https://github.com/microsoft/typescript GitHub servers and GH Action runners run on Azure: https://cnbc.com/2022/10/12/microsoft-github-relying-more-on-azure-cloud-services-scott-guthrie.html
npm, Azure, XBox, ChatGPT, Copilot, DALLE, Playwright, Blizzard and all of their games.
Btw, dotnet, C#, and especially F# are not 100% developed by MS. There are thousands of pull requests from random people from around the world.