Some users post copy of theri blog post to other blogs. Then exactly same copy (same title, author, content) appears in planet.jboss.org.
Example:
https://planet.jboss.org/post/teiid_8_8_beta1
https://planet.jboss.org/post/teiid_8_8_beta10

One way how to improve this situation is to allow only one blog post with same title and author (RSS author).