Currently, documents, % Complete and Status data can be retained when moving or copying a task from one project to another. Updates at the project level will migrate if a full task list is selected, but Updates at the task level do not.
If work starts on a large project and the PM wants to split the work across multiple projects instead to make is easier to manage, losing those discussion threads can be a significant problem. The manual solution of taking screen grabs or copying/pasting the threads - one task at a time- is not very efficient.
If there is an option to preserve other task-based data from Task Move or Task Copy actions, why not Updates?