Of course! That's because <b>Google forces group members to post duplicates</b>.
See for example the <a href="http://www.diigo.com/06tij">complaints from users</a> at <a href="http://groups.google.com/group/Google-Groups-Basics/browse_thread/thread/bcbbac7dfa31076d">Google Groups Basics > No reply option !!!</a>
* very inconvenient
* really confusing
* discouraging
* very annoying. - Graham Perrin on 2009-08-11