When does auto dismiss to watchface occur?

The behaviour should be:

• Auto-dismiss new messages unless you interact with the message
  
• Auto-dismiss from the launcher (as this can happen if the button gets accidentally pressed twice in a row)
  
  

but otherwise it should stay on the app.

If messages doesn't auto-dismiss, are you sure you wouldn't have interacted with the showing message in any way? I did merge some changes recently to improve the way it works so if you're running an older version of 'messagesgui' you might find it's fixed now - or perhaps if you have a the new version it might have been broken :)