Tbh I thought it was a bunch of non-lemmy platforms (e.g., mbin which fedia.io runs - anecdotally it usually happens due to some types of edits not federating well), but if someone from infosec.pub (which runs lemmy) also had the problem then I'm actually not sure what the common factor is lol

edit: the common factor might just be instances that have blocked lemmy.ml, which currently includes fedia.io (my instance) and infosec.pub (the other commenter's instance), though I'm surprised links to lemmy.ml's hosted images are included in the block