The image is hosted using lemmy.today's pict-rs server rather than lemmy.world's. Not that there's anything wrong as such with that -- I mean, I use lemmy.today, and Lemmy will let you link to an image wherever -- but AFAIK, the lemmy Web client always uploads using the home instance of the submitting user, doesn't have an option to do otherwise.
When I first noticed that the image was hosted on lemmy.today, because my home instance is lemmy.today, I thought "Oh, cool! There's some sort of local-instance-side caching that's been added to lemmy to propagate images!" I figured that it was just on lemmy.today because that instance is my home instance, and it had propagated. That would potentially -- depending upon implementation -- close a hole where lemmy exposes user IP addresses that I'd commented on before. But...no, even viewing the post on lemmy.world also has the image being hosted on lemmy.today.
Just out of curiosity, @[email protected], is there some sort of lemmy client that permits creation of a post using one Lemmy server's pict-rs instance but the post itself to go to another lemmy server? Or did you need to manually upload on lemmy.today prior to creating the post on lemmy.world?
What's changed, at some point prior to now, is that lemmy started propagating images, not just posts. It didn't used to do that -- one of the first conversations I dropped into here was one where Ada, the lemmy.blahaj.zone admin, was talking with someone in the Middle East, in a majority-Muslim country that did not like LGBTQ content. Their country had blacklisted lemmy.blahaj.zone -- a trans-oriented server -- at a national firewall level. They could view the text content on lemmy.blahaj.zone by using a different home instances federated with lemmy.blahaj.zone and viewing the posts and comments as they propagated, but couldn't view the images that users there had posted.
Hopefully lets lemmy scale more -- you don't have one user post an image to their home lemmy instance and then have everyone beat that server to death.
Thanks! Sorry for the confusion, but it's probably good that it works this way now.