My response as follows:
I haven't read all the replies yet, but one thing comes to mind as a distinguishing factor when I explain to others how I differentiate professional from para-professional and it doesn't really have anything to do with the list mentioned here. I was one of those who pooh-poohed the idea of MLIS while working in a library as a page with master's degree in literature at minimum wage. After receiving my MLIS, of course, I had a different take on the whole thing. Making more money was a big incentive for supporting getting the degree for me, but in getting the degree I made a commitment over and above the one I had prior to the degree. I made a commitment to consider the role model associated with the title, a commitment to supporting lifelong learning not only for myself but for everyone, a commitment to not make assumptions but rather "look it up" (research) and provide supporting statistics when possible. I could go on, but suffice it to say that with the "commitment" to the field came the "professional" standing, not just the degree. For para-professionals, being a librarian (one who works in a library) is often about a "job" rather than a vocation. It's more like "a calling" for those that choose to make the commitment to be a professional librarian, though, as in any field, the degree is only one step of the journey. We practice our academic skill set and learn from our day to day experience, all the rest of the numbered items are of consequence only in this regard.