Clarify performance note

editions/tw5.com/tiddlers/widgets/ListWidget.tid

@@ -117,7 +117,7 @@ Displays as:
 </$list>
 <<<
 
-Note that using the `index` attribute degrades performance because it prevents the list widget from being able to optimise refreshes by moving list items around instead of rerendering them.
+Note that using the `index` attribute degrades the performance of the list widget because it prevents the optimisation of refreshes by moving list items around instead of rerendering them.
 
 !! Edit mode