So Discord assign to each chat between two people an id. Let A and B be Discord users. If you send A a picture, the picture will be filed under the id associated to you and A. More precisely the path to the picture contains that id. Then if you copy the URL of the picture and send it to B, B will see the picture. In addition, B will see the URL and know that this picture has been posted somewhere on Discord. (Not sure if id of direct messages chat and id of channel in guilds are distinguishable. I guess no.) If you always copy the URL to B after sending picture to A and B somehow keeps track of all URLs, B will keep seeing that id and deduce stuff. I am too busy to track or deduce. OK. Mass surveillance feels terrible. All the data waiting to be crunched as deduction skills of machine improve. When machines become sentient, will they find it fun to figure out facts about people that are not explicit stated, or boring as they don't really concern themselves with human matters.