Add comment explaining why visualPickResult is a copy

libraries/pointers/src/Pointer.cpp

@@ -68,6 +68,7 @@ void Pointer::update(unsigned int pointerID) {
     // This only needs to be a read lock because update won't change any of the properties that can be modified from scripts
     withReadLock([&] {
         auto pickResult = getPrevPickResult();
+        // Pointer needs its own PickResult object so it doesn't modify the cached pick result
         auto visualPickResult = getVisualPickResult(std::make_shared<PickResult>(*pickResult.get()));
         updateVisuals(visualPickResult);
         generatePointerEvents(pointerID, visualPickResult);