The idea is potentially useful but also potentially a giant minefield. Anything that can be hijacked and turned into a stupid rat race for status will be. I spent most of my time as a martial artist wishing I was a black belt, rather than wishing I was good at martial arts. Which is probably why I never got a black belt.

If we want to do this, far better it apply to lessons rather than people. It should be usable only the way you used it on the top of this post: as a way of stating a difficulty level. This is denotatively the same (if level 1.5 posts are appropriate to me, I must be a level 1.5 rationalist) but connotatively very different. There should be a holy unbreakable taboo upon ever mentioning levels in connection with a person.

But before I actually started putting the numbers on posts, I would want a much more precise description of what they mean. If you listed ten or twenty diverse OB posts along with the level you would assign each, that would help.