Ah, you're right, I forgot the XHTML part.
Anyway, IMHO it's better to have a separate PR for this.

SVN commit 668552 by okellogg:

Add selector for comment in template matching <UML:Attribute>.
BUG:145972


 M  +1 -0      ChangeLog  
 M  +1 -1      umbrello/docgenerators/xhtmlgenerator.cpp  
 M  +6 -0      umbrello/docgenerators/xmi2docbook.xsl  


--- branches/KDE/3.5/kdesdk/umbrello/ChangeLog #668551:668552
@@ -5,6 +5,7 @@
 * Crash on deleting class in list view (145762)
 * Class attribute documentation not generated for python (145916)
 * Python code generator does not wrap lines properly (145918)
+* Attribute documentation not generated for 'Export to XHTML' (145972)
 
 Version 1.5.7
 
--- branches/KDE/3.5/kdesdk/umbrello/umbrello/docgenerators/xhtmlgenerator.cpp #668551:668552
@@ -1,5 +1,5 @@
 /***************************************************************************
- *                        xhtmlgenerator.cpp  -  description             *
+ *                        xhtmlgenerator.cpp  -  description               *
  *                           -------------------                           *
  *  copyright            : (C) 2006 by Gael de Chalendar (aka Kleag)       *
  *    (C) 2006 Umbrello UML Modeller Authors <uml-devel@uml.sf.net>        *
--- branches/KDE/3.5/kdesdk/umbrello/umbrello/docgenerators/xmi2docbook.xsl #668551:668552
@@ -666,6 +666,12 @@
       <xsl:value-of select="@name"/>
       </entry>
   </row>
+
+  <row>
+      <entry role="comment"/>
+      <entry namest="c2" nameend="c3" role="comment"><xsl:value-of select="@comment"/></entry>
+  </row>
+
 </xsl:template>