Flutterby™! : Unicode hidden data

Smuggling arbitrary data through an emoji. Abusing Unicode to stash arbitrary data in characters, that persist across copy and paste. In particular, this raised an eyebrow:

There are techniques for using subtle variations in text to “watermark” a message, so that if it is sent to a number of people and then leaked, it’s possible to trace it to the original recipient. Variation selector sequences are a way to do this that survives most copy/pastes and allows arbitrary data density. You could go so far as to watermark every single character if you wanted to.