Technically, formatting rules like these can be described using SGML short references, which then serve to replace those tokens by start- and end-element tags i

Technically, formatting rules like these can be described using SGML short references, which then serve to replace those tokens by start- and end-element tags into angle-bracket markup (SGML, XML, HTML). Works for block quotes, too, as tokens scanned for replacement can be anchored at line beginnings (can include "record start" and "record end" characters). Though I'm not aware of a modern MUA employing SGML ;(