Comment by orangepurple
4 years ago
In digital typography, combining characters are characters that are intended to modify other characters. The most common combining characters in the Latin script are the combining diacritical marks (including combining accents).
Specifically _Vietnamese_ combining characters. The Vietnamese writing system uses multiple combining characters at a time, and stacks them vertically. Throw in a few that wrap around the character like t҉his, some 𝑎lternatᵉ lꬲttꬲr fᵒrms, disturbing imagery, and perhaps a few other tricks, and you have zalgo. See also https://stackoverflow.com/a/1732454/823846