For one. I have no idea how to remove specific posts from "What's new". I imagine that figuring that out would take far more time than it's worth.
When new items are added (those that don't have a thread already), they will be added in BARcode and it will, in turn, create the DBTC thread. We don't want those posts suppressed for obvious reasons.
When an existing item is imported - which is what's going on now, BARcode posts to the existing thread. I don't believe these posts are useless. They tell anyone in the thread that the item is now in the system and they can go look at it there. These posts also raise awareness of the item...I had no idea some of them even existed.
This is a temporary "problem". It is due to the tremendous effort that
@Coral reefer has put into importing threads in the past few days. It will go away organically. At some point, all threads will have been imported and you will never see it again.