I think it might, spamming same meme images over and over is quite common in some servers. On other hand the bigger pictures might overhelm these just in size.

Yeah, that's why I assumed it wouldn't help that much. People re-upload 100kB memes all the time, but the bulk would probably be 5MB phone pictures that won't typically be re-uploaded.

The plural of anecdote isn't data, but about 20% of the images I post on Discord come from Discord in the first place, cross-posting among different servers.