The forum acts as a proxy for all embedded images. This is a privacy feature to disable
tracking pixels, but it's also slow. I've seen threads where people replied without having seen the images, thus missing valuable information.
I only thought of using alt-text today, and this works. While the image is still loading, my post can show a message about it.
Example[img alt=Image loading...]https://bitcoin.org/img/icons/logotop.svg[/img]
Shows
(press Shift-reload to see it in action)
My suggestion: is it possible to set this alt-text as a default for all embedded images?
Throbber test[img]https://bitcoin.org/img/icons/logotop.svg[/img]
Shows
Update for (manual) further improvements to embedded images: if you set the exact image size, the post "reserves" the required space even before the image is loaded.
Example:[img width=190 height=40 alt=Image loading...]https://bitcoin.org/img/icons/logotop.svg[/img]
Shows
(press Shift-reload to see it in action)