(define-key global-map (kbd "C-h") 'paredit-backward-delete)
(global-set-key (kbd "<f11>") 'rename-buffer)
こんな感じでC-j上書きしちゃえ

Lisp function in `paredit.el'.
It is bound to C-j.
(paredit-newline)

(let ((n (frobbotz))) |(display (+ n 1)
port))
->
(let ((n (frobbotz)))
|(display (+ n 1)
port))