Index: src/main/java/org/xwiki/rendering/renderer/xhtml/XHTMLRenderer.java
===================================================================
--- src/main/java/org/xwiki/rendering/renderer/xhtml/XHTMLRenderer.java	(revision 11896)
+++ src/main/java/org/xwiki/rendering/renderer/xhtml/XHTMLRenderer.java	(working copy)
@@ -122,6 +122,15 @@
                 // Thus we use a class instead so that it can be styled using CSS.
                 print("<span class=\"underline\">");
                 break;
+            case SUP:
+                print("<sup>");
+                break;
+            case SUB:
+                print("<sub>");
+                break;
+            case MONO:
+                print("<tt>");
+                break;
         }
     }
 
@@ -148,6 +157,15 @@
                 // Thus we use a class instead so that it can be styled using CSS.
                 print("</span>");
                 break;
+            case SUP:
+                print("</sup>");
+                break;
+            case SUB:
+                print("</sub>");
+                break;
+            case MONO:
+                print("</tt>");
+                break;
         }
     }