When I set in NDoc GUI the DocumentProperties tag to true, the Serializable attribute is duplicated in class summary page. May be the reason is inheritence of this attribute from the base class, but I set the DocumentInherittedAttrubutes tag to false. So, the duplication of this attribute must not appear, but it appears.
I use NDoc 1.3.1, MS 1.1, invoke NDoc GUI, and prepare results in MSDN help file.
The archive contains a test C# project with one empty class and NDoc project with documentation results