A long turn is hard to read as a pile of individual edits. The person receiving it wants to know what moved before they open every change.
Each redline turn includes a summary of what changed. The summary sits with that turn, so the incoming draft has a short account of the revision before the line-by-line markup.
Comments in the history can be replied to. A question about a change stays on that history instead of starting a new thread somewhere else. Show more and show less keep a long history from taking over the panel, while the replies remain attached to the comment they answer.
