Because I'm fairly annoyed at the way some approvers choose to approach this feature, I've decided to open up a new topic separate from topic #14063 describing what I personally think is wrong with this approach.
The post replacement feature was something originally developed to replace image samples only, so that the post index wouldn't be cluttered en masse with explicit 1up replacements and we wouldn't have to resort to moving favorites (that which isn't perfect even right now). Yet it is now used in a multitude of cases, both of which may be fairly justified or unjustified:
- A user uploaded the wrong image (say, a thumbnail or site asset, or the wrong image in a gallery set) and an approver forgives that mistake by replacing it with the correct image. This is fine.
- Corrupted images -> uncorrupted images. Also fine. About par since corrupted images are also unconditionally unwanted.
- An approver replaces an "inferior" image with a "superior" image, sometimes with and usually without checking for integral superiority in every single aspect of an image file's quality. Sometimes the image doesn't even share complete visual identity, putting aside compression artifacts.
There have been a number of cases where an approver has went out of their way to replace images that were actually worse than their original counterpart without checking, or inherently different, however. In that respect, I'd like to clear up why we shouldn't do the third case, and stick to the normal way of 1upping or supplanting Twitter uploads with their "superior" Pixiv counterparts.
- It messes with repost bots. This indirectly harms an image's survival in other imageboards. In the case that ours is eventually lost through either an artist requesting a hard deletion of all their work, if no one catches it then, it is gone for good. And even if we still have it, it harms the artist's exposure.
- It messes with IQDB and SauceNAO. Again, an unintended effect of the post replacement feature since they have to re-index whatever gets replaced.
- Some users prefer alternate sources, simply because it's easier to share a user's work that way. A somewhat unique case, but it is one nonetheless.
- Cases where a Twitter image, or an image from another inferior site would be considered superior in at least one other criterion listed in help:post relationships, or other similar criteria listed as such.
- Notably if a Twitter image (PNG, RGBA32) is better compressed than one from Pixiv/Seiga/Tumblr/whathaveyou. See post #2844376.
I have finished a writeup a few months ago on this in topic #14426, about which "duplicates" we want to keep. Specifically in this area. There are numerous cases where detecting if an image is revised without doing a layer comparison is difficult and not immediately obvious. See post #2851989, post #2863296, and post #2767376 (along with their respective children).
post #2767376, in particular, is interesting because the pawoo counterpart image sources are no longer alive. And they were different than that of the pixiv versions (as the pixiv versions had the palm tree in the background drawn in after, whereas the pawoo images didn't have them at all or were drawn in differently). Of course, I would say they are now "long lost" but luckily gelbooru has them saved because of their repost bots.
It's a great example in particular, because it describes to the extent which human error goes in regards to comparing identity with images. Let me draw this out with one of them.
- post #2767376 was originally this image on gelbooru (direct link). Note the MD5. It was replaced with a visually similar but non-identical image, that of which was NEVER reuploaded. This would have never happened had this sort of replacing not become a norm.
- post #2768213 was this image on gelbooru (direct link). Note how the palm tree is drawn in differently on both images. Again, same as above.
While I don't disagree with the notion that it's great to have less duplicates on the server, the fact is simply that we cannot trust ourselves to do otherwise because it will eventually lead to the sort of case where if we're not careful, we'll be replacing totally fine images with images that are potentially worse. What if somebody replaces an image uncensored on twitter/pawoo with an image censored on pixiv? And if no one notices until months, perhaps years later, long after the original source is gone?
The fact is that while duplicates are not preferred, I prefer having duplicates over inherent human mistakes any day of the week. This sort of impromptu duplicate superseding and "removal" is subject to mistakes that are simply out of our control lest we go through an arduous check of everything concerning an image's quality, no matter in what respect it is. The reason why replacing samples and corrupted images, or replacing the wrongly uploaded image with the right image is accepted is because we can confirm, with zero doubt in our minds, that the previous image was unwanted. Samples and corrupted images will ALWAYS be worse than their original counterparts. You cannot say the same for this.
More importantly, why change a system that's worked completely fine in regards to 1upping other users? If you upload from Twitter, you basically accept the risk that your post will be superseded by a superior post if it is reposted somewhere that doesn't resample the original image. It's better than always having to quickly check for visual identity and then have to check the file quality or information present also.
Anyways, I'll have more to bump this topic with, but I recently got a new phone in the mail today and I have to set that up.
Updated by Mikaeri