Comment by ptero

Every system has bugs, even deployed, high visibility accounting systems. Debian stable, which I personally view as the gold standard for a robust general purpose OS, has hundreds of bugs.

That is not to say that bugs are good. They are bad and should be squashed. But the Horizon failure, IMO, is with the management, that pretended that the system was bug free and, faced with the evidence to the contrary, put the blame on postmasters. My 2c.