jsfiddle/OpenLayers.debug.js
function(pixel) {
                if(this.feature === control.feature) {
                    this.feature = control.box;
                }
                OpenLayers.Control.DragFeature.prototype.moveFeature.apply(this,
                    arguments);
            }
function(pixel) {
                if(this.feature === control.feature) {
                    this.feature = control.box;
                }
                OpenLayers.Control.DragFeature.prototype.moveFeature.apply(this,
                    arguments);
            }
function ( pixel ) { if ( this . feature === control . feature ) { this . feature = control . box ; } OpenLayers . Control . DragFeature . prototype . moveFeature . apply ( this , arguments ) ; }
avoid moving the feature itself - move the box instead
avoid moving the feature itself - move the box instead