Shoutbox

sounds good to me ...

or maybe make the default even "/" like in plus, then the analogy with Plus! and the double forward slash is totally complete? (and the user must already type / for commands to work, so....)

PS: Though double typing a delimiter to get the literal character has the disadvantage that you can not end the first part with the literal character. Because the last character of the first part and the delimiter form together a double character and thus will be interpreted as literal... You don't have that when you use an different literal "identifier"... But I can live with that