Read Be careful what you copy: Invisibly inserting usernames into text with Zero-Width Characters by Tom Ross (Medium)

Zero-width characters are invisible, ‘non-printing’ characters that are not displayed by the majority of applications. F​or exam​ple, I’ve ins​erted 10 ze​ro-width spa​ces in​to thi​s sentence, c​an you tel​​l? (Hint: paste the sentence into Diff Checker to see the locations of the characters!). These characters can be used to ‘fingerprint’ text for certain users.

A cool little trick with text for embedded steganography, security, or other communication purposes.

This could also be used for pseudo-private communication via Webmention even. Just hide your messages inside of public messages.

ᔥ Aaron Parecki bookmark Be careful what you copy: Invisibly inserting usernames into text with Zero-Width Characters (medium.com) (2018-04-05)