It’s possible, hear me out here, to have more than one computer, you know.
I deleted this comment right after I made it. How did you see it, and how are you able to reply to it?
That’s the way the Fediverse works. When you post a comment, an update is distributed with your comment. Once you delete it, an update is distributed that you deleted your comment. Lemmy then still shows that there was a comment but it has been deleted. Federation delays could mean that they didn’t see your comment as deleted instantly. In theory, a Fediverse instance could also just ignore the deletion update and keep showing the deleted comment.