If the rules/algorithms are set and monitored by humans, the humans are the ones ultimately responsible. Computers are just tools which provide greater utility and control for investors than ever before.
That comes with its benefits and also with its potential downsides, but does not lessen from the fact humans are ultimate responsible.
One of the points that the article makes is that this statement is changing, that computers are increasingly creating their own rules. The literal next sentence:
"New artificial-intelligence programs are also writing their own investing rules, in ways their human masters only partly understand."
You're right though, that the responsibility still falls on the humans. Anybody running algos that they don't understand should ensure that they are covered from a legal/ethical perspective.
Apparently, none of the Nobel prize winners thought to model out that particular adverse condition.
Bunch of smart people + one missed market condition = failure (eventually).
If there aren't people involved at every step of the way to inject humanity into decision making processes, it's much easier for companies to hide behind their "algorithms."
I believe the blossoming buzzword for it may be Mathwashing.