It is because you selected DT as one of your favourite users. If you click the yellow star on any user's page, they will be registered as one of your favourites, which will make their posts and actions visible in the updates section.
If you go to DT's page, check the star. If it's highlighted, then problem solved, that's why it was shown. Otherwise, the site screwed something up for sure, or you are forgetting that you visited that question or Dark Kyurem's page and favourited one of them, but I guess that is unlikely.