This userscript unsquashes inline images in comments by fetching the source image and downscaling it to 50%.
Requires *monkey extension to run (greasemonkey, tampermonkey, violentmonkey, et al)
Edit: also updated it to support the thread index
without the script, you click on the thumbnail and it opens the thread, you click the thumbnail again and it opens the full image. But with this script, the thumbnail in the thread is gone and cant be clicked.
Here’s an updated version that should handle all scenarios