Thanks for the suggestion here. While notifying task creators when a task is completed a great idea, it's not currently on our roadmap for the next couple of quarters. For that reason, I am switching the status of this idea to Not Currently Planned.
We'll re-evaluate this idea in the coming quarters and update the status accordingly if anything changes.
Please implement this feature!! I'm surprised this isn't already a feature given that the Tasks function is so widely used and that this thread has been open for 6 years.
If a user assigns a task to another user, they should have the option to be notified when the task is completed. Otherwise, it adds unnecessary back-and-forth communication, which in some ways defeats the purpose of having automation.