This arose out of a discussion about the definition of a stub. I think it would be a very useful feature if there could be a little symbol, such as a small "i" with a circle round it, next to any link to an article that has been marked up as incomplete. Then readers would know that the leaf symbol meant "Don't expect to find any mathematical content here" and the incompleteness symbol meant "There will be at least some mathematical content here, but don't get your hopes up." I think this could be very nice indeed, and make navigation even smoother than it already is.