You have to be careful about those safe environments, as they often simply shift the weapons from loudness and brashness to sweet-sounding talk and subtle negative suggestions. It changes the breed of social warrior who wins from the "Conan the Barbarian" type to the "Mean Girls" type, but that doesn't help good ideas. One example of a dysfunctional strategy that only works in safe environments is the technique of subtly poking at someone's emotions until they say something off-limits or use an unacceptable tone of voice. Toxic individuals are always at work, and changing the rules sometimes does nothing better than changing the ruling toxic personality type.
There are many ways to implement "safe environments". I'm a person who easily speaks up and is pretty assertive but back when I worked in Scrum I really liked the retrospectives where people first silently wrote down their thoughts on post its, then each and everyone went and put them up; explaining what it meant. During this you were not allowed to disagree with but you could ask for clarification. Then you would vote on what seemed most important and go into deeper discussions.
I always felt that those sessions were more productive than just going around the table or people just speaking up.
That's a great point, and one I've seen in action. I haven't seen the particular strategy you describe, but I've seen others. People can absolutely weaponize efforts to create psychological safety. IMO psychological safety is a necessary, but not sufficient condition for being able to disagree about ideas and come to better ones.
I think great leadership is when someone notices that happening and shuts it down.
Goodhart's law applies to psychological safety. It is a good measure of a culture until people starts to actively work towards psychological safety. I feel like most of these tips and tricks people use to improve their social skills are just making it harder to rat out the toxic people, it doesn't actually make people less toxic.
