Just noticed I was having this problem as well. How embarrassing.
However, the problem seems to be with all image links and not just the ones edited by any one person in particular.
It appears the URL responsible for hosting the card images is either broken or down. By quoting the OP for Spark and reinserting the image URL according to the exact URL that is listed on the wiki
, and then previewing the post, it works just fine and the image is visible again.
I guess a simple fix would be for Masters to adjust the image URLs on the card threads to match the ones on the wiki? Not sure of what the problem is exactly so it's hard to say.