The Hacker News comment by GuB-42 delves into encoding an unlimited amount of data in a single emoji using ZWJ sequences or other Unicode characters. The concept involves converting bytes into variation selectors and concatenating them to encode data. Surprisingly, the hidden data remains invisible once rendered but can be decoded back. This can potentially be misused to sneak past content filters or watermark text with hidden messages. While intriguing and creative, the abuse of Unicode in this manner is cautioned against for ethical reasons. The technique showcases the complex yet fascinating possibilities within Unicode character encoding.
https://paulbutler.org/2025/smuggling-arbitrary-data-through-an-emoji/