Whether arbitrage or manipulation, the Jane Street episode highlights a critical truth: markets need more transparency, more accountability, and more human judgment.

Jane Street has been barred from the Indian securities market by its markets regulator, which has said the U.S. firm used its trading strategies to "manipulate" a key stock market index, leading to losses for millions of retail investors,

The drama has thrown a bright light on Jane Street, a company of legendary opacity even in an industry that prioritises secrecy. And it could carry political and regulatory consequences, not just for Jane Street,