> It'd be in a non-native language, like C#.

True; C# is the most obvious choice for Teams.

> JavaScript is faster than you think.

I'd be very surprised.

> Miles ahead of Python, Ruby, Perl, PHP.

Depends on "miles" - I think it is within the same order of magnitude as all of those. If it's far off from being in the same order of magnitude of those, I'd be very surprised.

> Not too different than C#/Java

I don't think so, not for idiomatic usages anyway. Java and C# are pretty damn fast! ISTR that Java/C#/Go are in a different order of magnitude from JS, Python, PHP, etc.

(The link doesn't work, btw)