(Do note that new users already have a grey username to let you know they joined in the last 2 days. We added that a while ago. So there is a tiny bit of context when you see a post by a user, if their name is grey and not a blue link, you know they are a new user.)
Indeed, but isn’t clicking “no” to the question “is this an appropriate contribution?” a negative action?
Sure, unless a few of your so-called trusted users are keen on telekinesis. 
Overall I like this mockup a lot, and it certainly makes sense as a way to get from trust level 1 to trust levels 2 and beyond. Curious what @frandallfarmer thinks.