"so they shouldn't be dangerous to the market, as long as they're designed correctly". Even if we accept the author's position, why would we also make the assumption that this software is designed properly and bug free?
I guess it depends on the stakes, and how well the traders understand (the risks of) software development to pay for the quality, testing, and maintenance.
"This isn't just some human lives we're playing with, this is serious! It could cost us billions!"
