What am I looking at and why is this here?

Seriously, the artifacts are worse than that of the twitter post, hell, it's far worse, and that's saying something. I don't think I've seen an image compressed this poorly in a really long time. Is this what jpeg-10 looks like? It's like a screencap from a hastily rendered Xvid encode.

I realize my comment is incredibly negative, but why upload an image from Pixiv when it is clearly and obviously worse than an identical image which has already been uploaded? It's not even the same resolution. I genuinely want to know the reasoning behind this upload.