It's old-school plain-text email etiquette. The original Markdown even used a va...

Jasper_ on July 18, 2020 | parent | context | favorite | on: Cloudflare was down

It's old-school plain-text email etiquette. The original Markdown even used a variant of that syntax for its links definition, known as "reference links". https://daringfireball.net/projects/markdown/syntax#link