Aximili23 writes:
[...] members could somehow sign up to belong to one or more of a list of categories, such as theistic evolutionist, atheistic evolutionist, young earth creationist, gap creationist, intelligent design proponent, etc.
I don't "belong" to a position, it's the other way around: my position belongs to me. Besides, my position might change. What you propose suggests too much rigidity for my taste.
Aximili23 writes:
In this way, it is immediately easy to tell what position each person subscribes to, especially when it isn't always clear from the post.
Suppose your categories were indeed listed, and somebody would write something unclear, then some people might say to themselves: "Well, this person belongs to category X, so they must have written something that's in line with X. Although I don't quite understand what they wrote, I won't bother to check by asking what they meant." You wouldn't want that to happen, would you? Because it would mean that discussions would be over before they even got underway.
If a person's position isn't clear from what they write, you should always ask for clarification. You might even learn something interesting.
We are all atheists about most of the gods that humanity has ever believed in. Some of us just go one god further. - Richard Dawkins