Both of those formats also work in comments outside of slash commands, are automatically linked to the respective entity, and label references are rendered as p

Both of those formats also work in comments outside of slash commands, are automatically linked to the respective entity, and label references are rendered as pretty labels, with their color and description tooltip. Using those characters also enables autocomplete in the Markdown textarea. In the web interface, they are very convenient, but they are not required, so when using slash commands with reply-by-email, you can leave them out and write exactly what you have under "Instead of"