Just now I noticed that post #1387659 was flagged for being by the banned artist nigiriushi. Disregarding that this is the wrong way to go about banned artists, I used the artist tag to add the missing artist but got nanoha instead of nigiriushi. The source Pixiv account has Takamachi Nanoha as the profile image and the artist name is ニギリ牛 (Nigiriushi).
Some posts, such as post #1041406, show up on nanoha’s Pixiv profile, so it’s probably safe to assume that they’re the same artist.
artist #26743 (nigiriushi) already lists two different Pixiv profiles and the third one should probably be added.
Unless aliasing takes care of deleting the images, all images tagged nanoha should be deleted.
Updated by Sal.N