The Fe users-INFJs at least-have actually noted at times feeling as though they were actually waiting for someone to invite them to post on threads-without that invite they dont feel comfortable speaking up-thus perhaps that is part of the reason there are not so many Fe threads.
Also-Your radar analogy gave me Ne orgasms. Really. It made my brain go ooooooo! and awwwwwww! It was a bit like the day my INTJ love compared Ni to differential geometry....*swoons*