I think this is just the nature of any open forum where everyone has an equal vote (democracy). In any large-enough population, there will invariably be a sign

I think this is just the nature of any open forum where everyone has an equal vote (democracy). In any large-enough population, there will invariably be a significant non-cognoscenti segment who will upvote this type of content. And who knows, for this segment, this content may be new despite repeated iterations elsewhere. It seems inefficient, but I'd rather have this type of system than systems that weight upvotes according to karma. This way, at least you avoid polarization by high karma users. The occasional low-quality content is not such a bad price to pay for a self-renewing system. After the hype dies down, there will naturally be fewer MNIST articles. :)