(I use the term "full reversal" to mean going from high confidence in a belief to high confidence in the opposite belief. A "hard reversal" is when a full reversal happens quickly.)
When have you noticed and remembered peers or colleagues changing their minds?
I think the question might need some modifiers to exclude the vast amounts of boring examples. Obviously your question does not evoke answers so boring as "Oh, the store is closed? Okay, then we can't get milk tonight" but what about a corporate executive pivoting his strategy when he hears business-relevant news? By now I am bored of Losing-the-Faith stories, but I don't deny their relevance to human rationality.
Anyway, I think full reversals tend to happen much less frequently than moderate reductions in confidence. Much more common are things of the form "I used to be totally anti-X, but now I see that the reality is a lot more complex and I've become much less certain" or "I used to be completely convinced that Y was true and the deniers were just being silly, but I read a couple decent challenges and now I'm just pretty confused overall". One way in which this happens is when someone accepts that their strong belief actually depends on some fact that they don't know much about.
But to try to directly answer your question, I might list:
- Megan Phelps-Roper left the Westboro Baptist Church, in part due to having respectful debates on Twitter
- Bostrom's Hypothetical Apostasy never really caught on, despite sounding pretty cool on paper. Too bad.
- Rationalists have gotten some recognition for anticipating the pandemic early--you might be able to find some good examples of mind-changing there.
- Rationalist-adjascent blogger Tim Urban had a fairly sharp reversal on cryonics.
- There's that classic (boring?) example of a person quitting grad school after spending a few minutes answering reasonable questions about their motivations.
- If you like getting mindkilled: Scott Alexander loosely identifies as libertarian, having formerly been vocally anti-libertarian. Seems like this happened via deliberate argumentation, including some email exchanges with David Friedman (son of Milton Friedman).
- I've seen some of my friends and acquaintances change their minds about psychoactive drugs.