RE: Why can't unset C-j in help mode like other modes?

[Drew Adams]

> I successfully unset C-j in other modes but the same trick doesn't
> work in help mode?!? Why is that?...
> 
> (add-hook 'help-mode-hook
>           (lambda () (define-key help-mode-map [?\C-j] nil)))

In *Help*, do `C-h k C-j'. You'll see this:

,----
| C-j runs the command View-scroll-line-forward
|   which is an interactive compiled Lisp function in `view.el'.
| It is bound to RET, C-j.
`----

Or do `C-h m' and look for LFD (which is `C-j'). You'll see that it is not
listed in the description of Help mode. You'll find it under the description of
View minor mode:

,----
| RET, LFD  scroll forward one line.  With prefix scroll forward prefix line(s).
`----

IOW, the `C-j' binding is not in help-mode-map; it is in view-mode-map.