Why was clemency trending last week?
A lexical convention due to Landin, allowing the scope of declarations in a program to be expressed by indentation. Any non-whitespace token to the left of the first such token on the previous line is taken to be the start of a new declaration. Used in, for example, Miranda and Haskell.
[P.J. Landin "The Next 700 Programming Languages", CACM vol 9 pp157-165, March 1966]