If you walk through a high-performing agile team space, you'll hear a buzz about the product:
“Do you see this?”
"Tell me more about what you want."
“But that is part of the acceptance criteria.”
"We should do it this way."
What you won't hear is just as telling, especially on a not-so-high-performing team. Sometimes, you have to see the sideways glances and grimaces to know that things are not working well interpersonally. And, if things are not working well between people, then they also will not work well in the product. Conway’s Law (paraphrased: "The product architecture reflects the team's architecture") proves that.
In traditional team cultures, feedback has been the sole responsibility of the manager. On agile teams, it's more important for feedback to be peer to peer, because the manager doesn’t know the minute-by-minute details of what's going on within the team.
What if it were not only the sole responsibility of managers but also of the team itself to provide guidance for an individual's growth? Building feedback into the culture creates a team with members who have a stronger sense of responsibility for one another. They will self-correct interpersonal and work-quality issues better and faster than a traditional team.