New users: error starting Discobot tutorial

I am, thank you. Did you get into the tutorial via the notifications panel?

I’ve just found that starting the tutorial from the notifications panel does work. The thing that leads to an error is the tutorial link on our About page, which I took from elsewhere on Meta:

/new-message?username=discobot&title=Discobot%20Tutorial&body=%40discobot%20start%20tutorial%0A%0AHit%20the%20%27Message%27%20button%20below%20to%20launch%20the%20basic%20tutorial%20with%20our%20chatbot.

On clicking “Send message” here, the error appears:

Perhaps this link format/method is outdated…? Is there something else I could use here?