added a convenience method

core/src/main/java/hudson/AbstractMarkupText.java

@@ -96,6 +96,13 @@ public abstract class AbstractMarkupText {
         addMarkup(startPos,endPos,"<a class='lowkey' href='"+url+"'>","</a>");
     }
 
+    /**
+     * Hides the given text.
+     */
+    public void hide( int startPos, int endPos ) {
+        addMarkup(startPos,endPos,"<span style='display:none'>","</span>");
+    }
+
     /**
      * Adds a start tag and end tag around the entire text
      */