[signify1121]

I have worked for a big (probably more successful) competitor to Jane Street, that uses in its different offices C#, C++, possibly some Java that I'm unaware of, and for non-production systems a very large mix of everything under the sun (Python, R, etc.)

The idea that the language is part of their success is simply absurd. If anything having to have to develop and maintain an entire ecosystem probably slowed them down more than anything.

[mhluongo]

It can sometimes help with hiring early on. Pg's "blob" blog post comes to mind.

[mkl]

Blub: http://www.paulgraham.com/avg.html