Often our team members will propose new dates for tasks that may not work in the overall time line. The PMs negotiate with the user, and a fair portion of the time we find a way to keep the original planned completion date.
The only way to remove / delete the commit date is to unassign then reassign the resource. It does not take long, but is cumbersome. Adding the option to "reject" the request in-line next the "Change Planned Date to...." link, would be helpful.