That's like saying it's wrong to flank some plain text with underscores or asterisks if the UI is not parsing that into rich text; actually the parsing isn't necessary for successful conveyance of emphasis (and the convention predates such parsing). By analogy, parsing of the @username syntax into a ping isn't necessary for successful conveyance that the word is a username (although I'm not sure the convention predates parsing in this case).
Just as seeing underscores/asterisks is understood as "the author is emphasizing despite lack of formatting," seeing a leading at sign is understood as "the author is saying 'this word is a username' despite lack of ping."
That's like saying it's wrong to flank some plain text with underscores or asterisks if the UI is not parsing that into rich text; actually the parsing isn't necessary for successful conveyance of emphasis (and the convention predates such parsing). By analogy, parsing of the @username syntax into a ping isn't necessary for successful conveyance that the word is a username (although I'm not sure the convention predates parsing in this case).
Just as seeing underscores/asterisks is understood as "the author is emphasizing despite lack of formatting," seeing a leading at sign is understood as "the author is saying 'this word is a username' despite lack of ping."
That was always understood. I just didn't want confusion with the word dang.