Re: No more signature images

Why not write a server side script that would allow users to input ad-hoc an external image link, it would then be tested for various properties (i.e. the size of the file, whether it is a valid image file, whether it is a dynamically generated image, whether it obeys the dimension restrictions) and if the image passed the criteria, permission would be given to the post parser to display the embedded image. If not, then the image would not be embedded.

When the images are external, the image itself can always be replaced later. So just because it passes today or tomorrow, in 3 days, I could keep the same image url, but the image itself is different. The only solution is local images or no images. Otherwise, there truly is no guarantee.

I'm aware of that. Read the second part of my post again.

Your entire idea blows up when you consider that the image could be dynamic. That means that a script generates it. Scripts can be told to always serve the exact same image to the forum server when it's checked. At that point, the only way to avoid IP address whack-a-mole is to put the image checker behind tor. Even then, the script can simply be told to serve the static image to any user behind tor, instead of the dynamic image, since that would only impact a small fraction of the people who would load the image.