Add comment about weird special handling of scene freeing in depsgraph.

source/blender/depsgraph/intern/eval/deg_eval_copy_on_write.cc

@@ -779,6 +779,9 @@ void deg_free_copy_on_write_datablock(ID *id_cow)
 			/* Special case for scene: we use explicit function call which
 			 * ensures no access to other datablocks is done.
 			 */
+			/* Not sure why this is needed? If id_cow scene has been correctly created outside of Main database,
+			 * then freeing it with regular BKE_id_free should properly *not* do any
+			 * children datablock user refcount manipulation... --mont29 */
 			Scene *scene = (Scene *)id_cow;
 			BKE_scene_free_ex(scene, false);
 			BKE_libblock_free_data(id_cow, false);