What is technologically possible but isn't being done?

Sorting replies on Twitter by some formula that pushes nonsense down and lets replies with substance raise to the top.

I have no idea why they don't do it. But replies to Tweets are a total shitshow.

A video game character that "lives" in a mirror, see

https://en.wikipedia.org/wiki/Pepper%27s_ghost

that can do sketch comedy with a human performer.