commit 073f8e7519a1bb08ae039f8b0b069efc32dc3388
Author: Steve Oliver <steve@circatree.com>
Date:   Sun Mar 31 13:54:56 2013 -0700

    This might work to get rid of the automotically added class attributes in template_preprocess.

diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index 8d527df..1e8a983 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -2645,9 +2645,6 @@ function template_preprocess(&$variables, $hook) {
     'title_attributes' => clone $default_attributes,
     'content_attributes' => clone $default_attributes,
   );
-
-  // Initialize html class attribute for the current hook.
-  $variables['attributes']['class'][] = drupal_html_class($hook);
 }
 
 /**
@@ -3121,6 +3118,7 @@ function template_preprocess_region(&$variables) {
   $variables['content'] = $variables['elements']['#children'];
   $variables['region'] = $variables['elements']['#region'];
 
+  $variables['attributes']['class'][] = 'region';
   $variables['attributes']['class'][] = drupal_region_class($variables['region']);
   $variables['theme_hook_suggestions'][] = 'region__' . $variables['region'];
 }
diff --git a/core/modules/block/block.module b/core/modules/block/block.module
index 42f22fa..0d9236b 100644
--- a/core/modules/block/block.module
+++ b/core/modules/block/block.module
@@ -550,6 +550,7 @@ function template_preprocess_block(&$variables) {
   // Create the $content variable that templates expect.
   $variables['content'] = $variables['elements']['#children'];
 
+  $variables['attributes']['class'][] = 'block';
   $variables['attributes']['class'][] = drupal_html_class('block-' . $variables['block']->module);
 
   // Add default class for block content.
diff --git a/core/modules/comment/comment.module b/core/modules/comment/comment.module
index dd87b29..0a322d5 100644
--- a/core/modules/comment/comment.module
+++ b/core/modules/comment/comment.module
@@ -1707,6 +1707,7 @@ function template_preprocess_comment(&$variables) {
   }
 
   // Gather comment classes.
+  $variables['attributes']['class'][] = 'comment';
   // 'published' class is not needed, it is either 'preview' or 'unpublished'.
   if ($variables['status'] != 'published') {
     $variables['attributes']['class'][] = $variables['status'];