Requested feature overview description.
A new metatag to filter reuploads. Specifically, a post that gets this tag would be a higher quality version of a previously uploaded post that got deleted pursuant to the upload of the higher quality version.
Perhaps something like isreupload:true.
Why would it be useful?
To filter out posts, which a user has already seen, from searches. For example, a user revisits an artist's gallery here after an indeterminate amount of time and wishes to hide new posts that are reuploads of posts they have already seen. Such a metatag filter would not be a perfect solution, but it's much better than guessing. I have been in this situation a few times.
To filter out the flood of Tumblr _raw reuploads (complaint thread ). Currently, I don't believe there's a good solution for filtering out only _raw reuploads without also filtering out new _raw posts that aren't reuploads. Such a metatag filter would address this issue well.
The idea is to only show new art.
For posterity, the Tumblr _raw discovery thread.
What part(s) of the site page(s) are affected?
All post searches could be affected, so https://e621.net/post/index.
Also, once implemented, the metatag would conceivably be toggled true on reuploads after site staff accept FFD requests for older, inferior posts.
Issue 1: Superior Reupload or Inferior Repost?
This metatag should only be true in cases where the superior post has a higher ID # than the deleted post. This avoids falsely marking old posts as reuploads when a lower quality version is uploaded and deleted later.
Issue 2: Retroactively Adding the Metatag
I'm assuming posts' reupload status isn't recorded cleanly in the database, but I could be wrong.
To find old reuploads, search for flagged and deleted posts with Inferior version/duplicate of post # in the reason field, like so. Should be straightforward to script toggling the metatag true as appropriate from there.
To find older reuploads from before that text was standardized, search for flagged and deleted posts with post # in the reason field, like so. I think it would be safe to script this too after extracting the post ID from the reason field and comparing it against the ID of the deleted post. If the post with the higher ID isn't deleted, then it's a reupload. Further, this is probably still safe for flag reasons that only show # followed by a number without the word "post", like so.
To find older reuploads with poor FFD reason formatting, try searching the reason field with a regex that just looks at what a post ID could be.