Person wants to remove a duplicate resource line from the activity.

Do not remove the line that was originally showing actuals. That line seems to be the line that was charged in timesheets and removing it would have a negative impact on timesheet data. Assign his Rate Source as coming from “Resource” so we can have the right rate going against the actual hours that will be charged. After you do that, it might be better to use the line the actuals are being allocated to as your resource line going forward. Make sure to zero out the budgeted and remaining units and add them to the line with the actuals. Tested some scenarios with duplicate lines and there is no real way to be sure that time entered to an activity with duplicate resource lines will roll up to the right line in Project Management once actuals are applied. Changing the finish date on the activity seems to allocate the submitted hours correctly, but I think using the line that is getting all the actuals will be easier to handle on your side.