This command has been present for a long time in StealthBot.
In version 2.7, the Alt combination hint (example: Alt-0046) in the response was replaced with the length of the trigger (example: Length: 1) when multiple-character trigger support was added.
How to use
Use this command by typing ?trigger in the presence of the bot. You do not need to know the bot's trigger, as that is the purpose of the command.
The bot will respond with the currently set bot trigger, in quotation marks, with the trigger's length in parentheses.