It's the same image quality as the twitter version by using Image Comparer to compare.

Although you can't tell the difference with the naked eye, Twitter still compresses the image.

Nope, twitter preserve jpeg image quality started from Dec 11, 2019:

Starting today, Twitter will preserve JPEGs as they are encoded for upload on Twitter for Web. (Caveat, cannot have EXIF orientation)

https://twitter.com/NolanOBrien/status/1204557498990002176

For 12Ko difference it's not necessary to repost the same one

I'd prefer having pixiv as the source, as sometimes I actually click that "source" link to find more from the same artist or to fix the tags.
Having twatter as the source isn't really helpful in that regard and perhaps should be considered as a secondary source if "better" ones, like pixiv, exist.

You can always click on the artist tag and look through the posts for finding different sources.

BattlequeenYume said:
You can always click on the artist tag and look through the posts for finding different sources.

Most often when I reach for the source link is exactly when the artist tag is missing, so that's a nonstarter.
Also, why use inferior sources in the first place when better ones are available?

vendiu said:
Most often when I reach for the source link is exactly when the artist tag is missing (...)

You can use the Find similar option on the left (when you clicked on a post) then.

BattlequeenYume said:
You can use the Find similar option on the left (when you clicked on a post) then.

Sure, but that has nothing to do with pixiv vs twatter as a source.

Well, we don't keep duplicates as soon as the image quality is the same. And first come rules.

You probably have to find a different site for that. I do agree to have a place to record various sources of the same art would be useful. That place just isn't here. Maybe one day we can have the system that supports multiple source fields