Fediverse

That is a general problem in the internet, not only in Lemmy, images andother content can be copied, this you can't avoid, it would even be imposible if you could delete embedded images in Lemmy, someone could have copied and pasted it somewhere else. But by using an imagesharer where you later delete the image, you also eliminate your origin as the author, since it no longer appears in your contributions in Lemmy or other sites.