Smuggling arbitrary data through an emoji

This Hacker News comment by GuB-42 intrigued me: With ZWJ (Zero Width Joiner) sequences you could in theory encode an unlimited amount of data in a single emoji. Is it really possible to encode arbitrary data in a single emoji? tl;dr: yes, although I found an approach without ZWJ. In fact, you can encode data in any unicode character. This sentence has a hidden…