small tweaks

no need to call toString() on the string
add comments

core/src/main/java/hudson/model/Computer.java

@@ -252,9 +252,11 @@ public /*transient*/ abstract class Computer extends Actionable implements Acces
         if (offlineCause == null) {
             return "";
         }
+        // remove header string from offline cause when a comment was set
         String newString = offlineCause.toString().replaceAll(
                 "^Disconnected by [\\w]* \\: ","");
-        return newString.toString().replaceAll(
+        // remove header string from offline cause when no comment was set
+        return newString.replaceAll(
                 "^Disconnected by [\\w]*","");
     }