Requested feature overview description.
It would be neat if, when you upload an image, e621 would check if a similar image has already been uploaded. Like an automatic version of http://iqdb.harry.lu/
If it finds an image (or multiple images) whose similarity to the upload is above a certain threshold, the upload process would be interrupted (but not aborted).
Maybe e621 could open the upload and the similar image(s) in new tabs, so the uploader can check for differences.
Or maybe add a "Reverse harry.lu Search" button the upload page.
It would be grayed out if no image to upload has been selected.
Why would it be useful?
It would cut down on reposts.
What part(s) of the site page(s) are affected?
https://e621.net/post/upload
Updated by Siral Exan