When a task is deleted a ‘task update’ is added to the comment thread area. Says “X user deleted the task,” just as it would when a task is moved to another section, assigned, due date added etc. It’s the ‘paper’ trail of the task.
You’ll see this when you go into deleted tasks and view the task.
However, if you undelete the task, this particular ‘update’ disappears from the tasks history. It then looks like the task was never deleted.
When a task accidentally or even maliciously is deleted this can affect the integrity of a task and this notation can be important to addressing an issue, whether explaining why something hasn’t been done yet, or inappropriate activity.
I don’t understand why a notation that was there would then be removed.