Since I can't make an appeal, I'll leave my appeal reason for this and the rest of the flagged posts as a comment on this post.

The jpeg artifacts are only apparent if you magnify the fullsize version by 400%. Also, I see a lot of images with jpeg artifacts that have gone unflagged for many years. Jpeg artifacts is a bad flag reason, unless it's very obvious and bad artifacting. If you're flagging this hoping that the artist is going to publish a version without jpeg artifacts, then I think that you'll be very disappointed. This has been up on pixiv for six months now, and the image is even worse on twitter. You either take this or you take nothing. I think that this and all the other flagged posts are drawn well enough to deserve to avoid deletion.