Fixed tree positions for siblings that have children under them

boards/models/thread.py

@@ -291,10 +291,14 b' class Thread(models.Model):'
                 for depth, element in tree:
                     index += 1
                     if element in parents:
+                        found_parent = True
+
                         offset_under_parent = parent_positions.get(element, 1)
                         tree.insert(index + offset_under_parent - 1, (depth + 1, reply))
-                        parent_positions[element] = offset_under_parent + 1
-                        found_parent = True
+
+                        # Move whole parent tree by 1 added element
+                        for parent in parents:
+                            parent_positions[parent] = parent_positions.get(parent, 1) + 1
 
             if not found_parent:
                 tree.append((0, reply))