"Twitter founder and CEO and billionaire Jack Dorsey... says he eats only one meal a day in the week and doesn't let any foodstuff pass his lips at the weekend."

"He also starts every day with an ice bath. 'Nothing has given me more mental confidence than being able to go straight from room temperature into the cold,' he says. And, rain or shine, he walks the five miles from his home to his office.... Dorsey's wellness-hacking habits are extrapolated from the ancient Greek and Roman philosophy of Stoicism.... [Dorsey has] created a platform that has allowed populists, alt-right types, and Russian bots to spread their messages to vast new audiences.... Twitter undeniably helped make Donald Trump president and gave Britain's Brexiteers a stage.... Dorsey has experienced how easy it is to create global pandemonium with a laptop and a smidgen of chutzpah. So for the Twitter CEO and his kind, trying to control biology with low-grade torture, plus a disinterest in traditional rich-people trappings, may be a kind of self-imposed penance for having built platforms and technology that have unleashed some pretty bad things on the world...."

From "Why are Silicon Valley billionaires starving themselves?" by Susan Margolis in The Week.

I don't believe there's any true penance here other than a desire for good PR (in that it makes him look serious, hard-working, and lofty — almost saintly). But I don't believe he's doing these things because he thinks he's done wrong — only that he wants to defend his company's reputation and freedom from regulation. I would guess that he's genuinely motivated by the desire for good health and long life and fascinated by extreme and challenging ideas about how to get that. Some people are drawn to stringent routines, and there's a sort of magical thinking about rituals.

And I don't think the philosophy of the Stoics had to do with penance. It's not about the sense that you've done something wrong and need to make up for it.