The new global blacklist for anon users is very annoying for some users and it (sadly) has good reasons being active.
(Blacklist in this post always refers to the global blacklist for anon users!)
I found a way of reconstructing image URLs from the limited data available on blacklisted posts.
I already wrote a small userscript to display blacklisted images on direct links, you can find it here:
https://gitlab.com/TilCreator/userscripts/-/raw/master/E621%20anonymous%20blacklist%20workaround.user.js
For now the script only reconstructs images on direct linked posts (/posts/X) and not queries (/posts), but that is possible, too.
I highly encourage anyone to expand this script, because I rarely use the site without being logged in and don't have much spare time right now.
How it is done:
With the API it is still possible to get the file extension and md5 hash of blacklisted images and that is all that is needed for image link reconstruction:
http://static1.e621proxy.ru/data/ + first and second char of md5 + / + third and fourth char of md5 + / + complete md5 + . + file extension
Or directly in JS: 'http://static1.e621proxy.ru/data/' + post.post.file.md5.slice(0, 2) + '/' + post.post.file.md5.slice(2, 4) + '/' + post.post.file.md5 + '.' + post.post.file.ext
To get preview, sample or cropped URLs, add those after /data and change the file extension to "jpg":
so http://static1.e621proxy.ru/data/preview/ ... .jpg for example.
Notes for reconstructing the /posts page:
The API endpoint (/posts.json) returns md5 and ext of blocked images, too, so one just has to search the API for posts where file.url is null and add the reconstructed preview URL to the website.
Updated