To clarify, the linked article does not claim that antimatter and matter do not annihilate one another (in fact, it reinforces such an idea). What it does claim is that the forces between antimatter's elementary particles, in this case antiprotons, are very simar to the forces between normal matter particles (protons). This leads to questions about the relative abundance of matter and antimatter in our universe, namely, why there is so much matter and (apparently) so little antimatter.
EDIT
This has already been clarified, sorry for the repost