I made a poll to see if anyone can (like D-Machine or jhedwards) actually see a superimposed image and not just "see" a superimposed image: https://news.ycombinator.com/item?id=49469365

See also Reddit, there has been lots of discussion and some similar polls. E.g. https://www.reddit.com/r/hyperphantasia/, and https://www.reddit.com/r/hyperphantasia/comments/kkbxom/when... for the specific poll.