We routinely need to delete Tasks from a Project that are not applicable to it, or whole Projects with Tasks that got setup unnecessarily or incorrectly. These come from templates we use, Request Forms, and from imported Projects. They always have Assignees attached to the Tasks. And these Users don't need to be bothered with receiving the email that their Task, which they hadn't even known about yet, was just deleted. It's just more email noise.
We expected to be able to turn those off with the Email Notification Option for when a "Task is added or removed from a Project or Folder", and have that Option un-checked — turned OFF. But that's not what that one does. It only applies for when a Task/Project is moved from one folder to another. Not the same thing. Please see support request #555791 – Email Notifications for Event Not Checked
So we suggest adding an Email Notification Option for when a "Task or Project is Deleted". If other Accounts, down to the User level, still want to get a Notification about it — if their process rarely includes deleting Tasks — they can leave it checked. We can un-check it and reduce some of the email clutter.
While your at it, relabel the existing Option to be more like what it does — maybe "A Folder Tag is added or removed from a Task or Project".
Also, while in there, add this same functionality for Inbox Notices when you do an upgrade to that feature. Please see: Editing Notification Types in the Inbox