Here's an example. I'll escape the markdown so you see the raw text:
:quality(80):no_upscale()/2018585659_8_1_230614_022120-w1920-h1280)
The URL contains unescaped parentheses which are illegal in a markdown link because the link itself must be wrapped in parentheses.
This results in my comments showing no pictures and users only seeing this nonsensical text:
:quality(80):no_upscale()/2018585659_8_1_230614_022120-w1920-h1280
If I try to escape the parentheses, I get this:
Oh, hey, it's the picture!
Whatever admin or bot is editing people's comments when moving pictures to some other host needs to escape special characters in the URLs.