As I recall, this is severely limited in that it does not correctly support sub-searches or pivoting between different indexes. Any news on if this has been improved?
Ouch. If Troy Hunt of all people can make this mistake, it can happen to anybody. HIBP is an awesome service funded totally by donations, so it's too bad this happened. Of course Microsoft is happy to hide behind their confusing pricing model and let customers overpay for Azure without alerting them.
I would imagine part of the reason is because even if you have a trained COBOL maintainer, they still have to learn and understand the actual business logic of the application. Learning the language is not even half the battle. Maintaining old often undocumented code is a hard task in any language.