clarify limitations of collision detection while moving multiple shapes

src/app/tools/modeler/diagram-js/features/domainStoryRules.js

@@ -205,9 +205,17 @@ DomainStoryRules.prototype.init = function () {
     let target = context.target,
       shapes = context.shapes;
 
+    // The idea of this code is to make sure that if any of the selected shapes cannot be moved,
+    // then the whole selection cannot be moved. However, it actually only checks
+    // if the shape that is under the mouse cursor is over another shape.
+    // This is probably enough as a full detection over overlapping shapes might make it hard
+    // to move large selections
     return reduce(
       shapes,
       function (result, s) {
+        if (result === false) {
+          return false;
+        }
         return canCreate(s, target);
       },
       undefined,