Anders Hejlsberg, the lead architect behind TypeScript has created C# and J++ at Microsoft, and Delphi and Turbo Pascal before. It's safe to say he has some experience in designing languages.
J++ is one of the primary reasons I am so wary about using a Microsoft-invented language. "Embrace and extend" a well-used language with extra features (then make them only work well on Windows later) has always been a classic Microsoft strategy. If they could get away with it with Typescript, I'm sure they would try again.