delegate a task

Is there a way to delegate a task but still have edit privileges on it (user does not report to the user)?  I tried adding the 2nd user, but then they don't have ownership

of it in terms of who the task is assigned to (if I wanted to report on it),  when i make the assignee the owner, then I lose edit rights (so I can't add my user id back). 

This seems like there should be an easier way to fulfill this requirement.  Not sure why when i switch the owner, it automatically removes my id from the list of Users.