From: Jeff Walden <jwalden@mit.edu>

When the comment is to be private, style the textbox the same way Bugzilla does.

diff --git a/content/reply.css b/content/reply.css
--- a/content/reply.css
+++ b/content/reply.css
@@ -1,4 +1,10 @@
 #comment {
-  font-family:monospace;
-  font-size:larger;
+  font-family: monospace;
+  font-size: larger;
 }
+
+.private {
+  color: darkred;
+  -moz-appearance: none;
+  background-color: #f3eeee;
+}
diff --git a/content/reply.js b/content/reply.js
--- a/content/reply.js
+++ b/content/reply.js
@@ -124,6 +124,13 @@ var ReplyDialog = {
                        .getService(Components.interfaces.nsILoginManager);
     lm.addLogin(l);
   },
+
+  togglePrivate: function RD_togglePrivate()
+  {
+    let textbox = document.getElementById("comment");
+    let checkbox = document.getElementById("private");
+    textbox.className = checkbox.checked ? "private" : "";
+  },
 };
 
 window.addEventListener("DOMContentLoaded", ReplyDialog.initialize, false);
diff --git a/content/reply.xul b/content/reply.xul
--- a/content/reply.xul
+++ b/content/reply.xul
@@ -25,10 +25,8 @@
     <label id="comment-label"
            for="comment"/>
     <spacer flex="1"/>
-    <checkbox id="private"/>
-    <label id="private-label"
-           for="private"
-           value="Private"/>
+    <checkbox id="private" oncommand="ReplyDialog.togglePrivate();"
+              label="Private"/>
   </hbox>
   <textbox id="comment"
            rows="10"