I have a question about "jpeg artifacts in a png" problem for a long time. Sometimes jpeg artifacts on png are just because editor doesn't want add more artifacts on a jpeg image. Isn't it reasonable? If we don't like jpeg artifacts why we should bear double-compressed one? It's kinda ironic. I don't think it should be the reason for deletion.

For this one, the original file has heavy screening and jpeg artifacts, The result now is much better, so the uploader didn't wanna ruin it with jpeg artifacts (again).

I think so.
if you fix a jpeg image and used the the blur tool( like greyc) to reduce the jpeg artifacts.what would you save the result?
if you save as jpeg you well make new jpeg artifacts.
so i would save as png.

It used to happen to me too, and had to save as jpeg cos the result wasn't perfectly clean of artifacts.
I had to remember you that the "jpeg artifacts in a png" is limited or applied mostly to images of digital origin that could have been recompressed, or compressed directly to a lossless format. Or at least that is how it used ot be, as I don't know what cases would have been during my absence.

There was some discussion about this in the forum but I can't find the right thread.

Why would someone use JPEG in the first place while there is JPEG2000? At least we won't have blocky artifacts.
Edited:
For patents reasons? But I can use jpeg2000 with Imagemagik.

shebang said:
Why would someone use JPEG in the first place while there is JPEG2000? At least we won't have blocky artifacts.

Blame Microsoft.

why people keep using mp3? :P think about it.