When an image is horizontally reversed from what it 'should' be based on asymmetrical details of a character's design, such as reversed heterochromia or being depicted as left-handed when they are right-handed in all other images.
This tag is not for all cases of reversed heterochromia, though, rather more strongly-evident cases where the following is likely to have happened: Artists often flip their work periodically while drawing to make sure it looks right from both perspectives and the angles of the lineart are not slanted, and such images may be a result of them forgetting to set it to the correct orientation before publishing.
This is arguably distinct from artistic errors since it is not details within the image that are incorrect, only the formatting of the image itself.
