“Industrial espionage” is quite a charge to level against a recruitment firm. But that is exactly the case being made by global investment and trading firm Susquehanna International Group (SIG) in High Court proceedings in Ireland. Ostensibly, a number of traders left SIG prior to 2015 to work for a rival firm called Citadel. So far so normal. But things aren’t as simple as they seem, according to Susquehanna, the quantitive trading firm which has its European headquarters in Dublin and pulled in core revenue of over €2 billion last year. And like the markets, the case itself has been…