I've noticed on 4chan's /b/ that people can flood a thread with delayclose.jpg, often uploading just a few seconds apart. Yet I can't even upload two different pictures to two different threads without setting off flood detection. What kind of evil magic are they using?

They usually do this to sage a thread, but it must be keeping the sage from working, because those threads are usually on the front page. Probably because sage doesn't actually lower a thread, it just doesn't bump it. So what they're really doing is "LOL THIS THREAD IS POPULAR WHICH MEANS I'M INCONVENIENCING LOTS OF PEOPLE! THE ULTIMATE GOAL OF EVERY 4CHANNER."