Append sibling node only when it doesn't already exist

CHANGELOG.rst

@@ -2,6 +2,7 @@
 
 Changelog for readability
 ==========================
+- Sibling node is appended only when sibling doesn't already exist.
 - Treat images a little differently so they get more inclusion.
 - Added User-Agent string into HTTP requests.
 - Added property ``Article.main_text`` for getting text annotated with

readability/readable.py

@@ -154,7 +154,8 @@ def check_siblings(candidate_node, candidate_list):
                 # filtered out later by accident.
                 sibling.tag = "div"
 
-            candidate_node.node.append(sibling)
+            if candidate_node.node != sibling:
+                candidate_node.node.append(sibling)
 
     return candidate_node