That would be good, but i wouldn't want another stream of notes to be stored with the task. We already have the Comments and the Description. To have a third place where a comment can be made on a task would reduce usability.
Would it work to do what you said, but to have the description associated with assigning the task entered as a Comment on the task, and for the comment to be prefixed with "User X reassigned this task to User Y"? For example:
Bob reassigned this task to Mary and made this comment:
Mary, I've done my bit, handing over to you for review and comment.
Similarly you could do something like the following when a task is marked Complete:
Mary marked this task complete and made this comment:
Bob, I've reviewed your work and agree the task can be marked complete.
And if it's reopened:
Bob reopened the task and made this comment:
Mary, sorry - just noticed something I didn't do quite right. Reopening so I can continue working on it.
Hopefully that makes sense? with the huge stream of notifications coming through, it would be helpful to have more contextual information provided with these actions.
Regards
David