lemmy is the mastodon of the threadiverse in that it invents a standard and expects everyone to follow it and because it’s the largest of it’s type you can’t really do anything about it
i bet what’s going on is that kbin is attaching images in the mastodon/microblog way and lemmy expects inline markdown images and doesn’t try to extract the attached images.
(fun fact: lemmy custom emojis are just “macros” for markdown images and not real emojis like the rest of the fedi standardized on (which is how you get things like the hexbear problem of remote emojis being gigantic))
i’d love to take a peek at a “glitch-soc for lemmy” but not that many people seem keen enough to fork and take on the responsibility of maintaining the jank.
that said i know of at least 2 instance specific forks (pawb.social’s and programming.dev’s), yet neither of them seem to have produced anything worthwhile just yet.