The other tweak that would help is making it truly one click, or adding text into the URL to explain to the green user that they must hit the ‘Message’ button. For example:
* [Start Basic Tutorial](/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.)