If you set the quality parameter to > 95% when creating a JPG from original picture, you won't be able to tell any differences between the PNG and the JPG, especially when the full width of the image is limited to max 720 pixels as it is on this website.
There is literally no reasons to prefer PNG over JPG in this specific scenario.
I have nothing against storing and sharing lossless images. But do it efficiently if you're gonna do it. Showing 10+ images that each weight a lot is not efficient. Instead, show the compressed image on the website (as it's limited to 720 width anyways), and add a link to the original. Now everyone is pleased.
I downloaded the 1.png file and converted it to a JPG and also diffed the origianl PNG with the JPGs I generated (90% in quality and 80%).
- Original PNG: 51M
- 95% JPG: 13M
- 90% JPG: 9.4M
- 80% JPG + interlace + strip Plane: 4.7M
Comparing the new versions with the original via the PSNR metric (closer to 1 is better [more similar]):
- Original PNG vs Original PNG: 1 (obviously)
- Original PNG vs 95% JPG: 0.999465
- Original PNG vs 80% JPG: 0.998611
With other (shorter) words: There is no difference for the consumer (a website visitor) between the two, except one uses more resources (RAM + network) and takes longer to download and the other one doesn't.
For the archiver (which you seem to consider more than the website user) there is clearly a difference between lossless and lossy files. But those can be linked instead of rendered directly inline.
There is literally no reasons to prefer PNG over JPG in this specific scenario.