Yeah, I heard about the reuploading thing. That could have been one way of doing some A/B testing. Although I think people back then did it mostly to get another shot at curation. Anyway, it's banned.

As to YouTube, I've only heard of creators tweaking titles and video thumbnails. But since they're doing that, I suspect they are not reuploading. I think on YouTube they just have a much longer window to try to get something to go viral and so it's probably more fruitful to tweak titles instead.