Channels read in time order
Messages in a team channel now read in the order they were written, so a reply sits under the message it answers.
A conversation between two people used to show each person's messages grouped together, so replies landed below messages that came later. Channels now follow the time each message was written, the same order on every Mac. A Mac with a wrong clock can only move its own messages, and never past a change in who is on the team.