When Assigned a task
When a task is assigned to you, create a Smart Group Tag with the Group called Assigned By and with the Tag the person name. Maybe the Tag need to be pre-pended by From: (ie From: Porky Pig)
I know you already display this in the various lists but it is not selectable to filter like Smart Groups and Tags are.
A benefit of the assignment of tasks for Managers is you can select the persons name from the People list when you meet with them, and see all the tasks you have assigned them (good for touching base). But for the person being met with they have no way to reciprocally see all the tasks the other person assigned them. The auto tagging would allow for this and allow for better task management overall.