> This post misses the IMO best indentation scheme for lisp [...]

Likewise, a lispier(?) and more compact compromise?:

    (define (match:element variable restrictions)
        (define (ok? datum)
            (every 
                (lambda (restriction)
                    (restriction datum))
                restrictions))
        (define (element-match data dictionary succeed)
            (and 
                (ok? data)
                (let ((vcell (match:lookup variable dictionary)))
                    (if vcell
                        (and 
                            (equal? (match:value vcell) data)
                            (succeed dictionary))
                        (succeed (match:bind variable data dictionary))))))
        element-match)