The source should be where the image was found. Simply changing the listed source doesn't change the image or bring back lost quality. If Pixiv has a better version, you upload the Pixiv version, not just change the source of an older, inferior version to pretend it's the better version.
And Pixiv is preferred over certain sources like Twitter BECAUSE Twitter will do compressions that drop image quality. If the current version is of the same quality, there's no reason to do anything.
The source should be where the image was found. Simply changing the listed source doesn't change the image or bring back lost quality. If Pixiv has a better version, you upload the Pixiv version, not just change the source of an older, inferior version to pretend it's the better version.
And Pixiv is preferred over certain sources like Twitter BECAUSE Twitter will do compressions that drop image quality. If the current version is of the same quality, there's no reason to do anything.
That's what I did initially, but Danbooru wouldn't let me upload it because it already existed (referring to this entry). So I figured that the images were identical and thus I just changed the source. I also figured that the reason that pixiv is preferred was partially because it has an English interface and was a more reliable source of an artist's artwork than other sources.
Personally, I find nicovideo to be a complicated site to try and use, and that's not only because everything is in Japanese.
That's what I did initially, but Danbooru wouldn't let me upload it because it already existed (referring to this entry). So I figured that the images were identical and thus I just changed the source. I also figured that the reason that pixiv is preferred was partially because it has an English interface and was a more reliable source of an artist's artwork than other sources.
Personally, I find nicovideo to be a complicated site to try and use, and that's not only because everything is in Japanese.
If it's the exact same image down to the checksum, then you don't need to do anything. It's not so much a preference FOR specific sites as a source, but AGAINST specific sources because, again, some sites like Twitter will perform lossy compression on an image.