Its 3There are three possibilities at this point:
Occam's razor would suggest that Barneyfag is the one posting the images.
- Barneyfag has trained an AI to recognize cropped derpibooru images and notify him when they're posted on 4chan, and also receives notifications for images with a hash that matches an image from derpibooru
- Barneyfag has memorized every single image on derpibooru, and can even recognize cropped versions of those images
- Anons are pretending to be barneyfag because they want to be banned for shitting up threads
- Barneyfag is posting the images himself
The guy uploaded his entire barneyfag folder years ago when he pretended to quit spamming as a way to trick bronies, so it's easy to replicate him. Not only that, but he'd actually respond to comments whenever you quoted him.