No, this is not a joke.

A law firm was apparently sanctioned $1000 for improper line spacing in a brief. The error was described as a deliberate act by the district judge.

https://www.law360.com/legalethics/articles/908332/susman-godfrey-fined-over-formatting-in-amazon-tm-suit?nl_pk=e1f033c5-3f89-4875-ad29-e0ddf85ed12c&utm_source=newsletter&utm_medium=email&utm_campaign=legalethics