Not only his fails do matter. His PROMISES that 'we have tested new features on the testnet very well' - that PROMISES do matter.
Yes, there was irrational overconfidence given the complexity of the system and the nature of software generally, but it
was tested lots and lots, about as much as you could with testnet as it was then, that's why they're now beefing up testnet. There are complex new innovations happening, hiccups are to be expected.
What Duffield says on criticism? When main bitcoin developer asked Duffield, he says like... 'Darkcoin is just project for FUN, like new Dogecoin'.
Source or GTFO. I think Evan would write better than that.
