Indenting of comments in emacs-lisp mode

Emacs-lisp mode indents comments based on the number of semi-colons prefixing them.
One semi-colon indents to column 40.
Two semi-colons indent to the same level as the block you are in.
Three semi-colons indent to wherever you place it and don’t move if you press <TAB>

;;; column:
;;;34567890123456789012345678901234567890123456789
                                        ; one semi-colon
(when (some case)
  ;; two semi-colons indents to the appropriate level
  (second line)
  )
;; two semi-colons indents to the appropriate level
      ;;; I want this comment to stay right here