Without firsthand knowledge of the Jane Street corporate environment it is naive of me to think that allowing engineering to pick the tools which best let them

Without firsthand knowledge of the Jane Street corporate environment it is naive of me to think that allowing engineering to pick the tools which best let them get their work done need not be incompatible with the requirements of non-expert review of the source code. I would think that if the company culture is one where it is expected that your code is going to be reviewed by domain experts, but not necessarily language experts, there would be a strong emphasis placed on producing source code which would convey its meaning without a detailed knowledge of the language spec and runtime system.