Editors generally support composing right-to-left languages that way? So I suppose the metaphor suggests that all editors should directly support the visible g

Editors generally support composing right-to-left languages that way? So I suppose the metaphor suggests that all editors should directly support the visible glyphs semantically? And yet, that's explicitly not the semantic purpose of those glyphs. The actual delimiters already exist at a lower code point. If we're asking editors to semantically support delimiters we should be asking them to support the semantic delimiters.