Re: `(' fontification.

[Richard M. Stallman]

    But this doesn't work, because in the actual value of `font-lock-keywords'
    this part has no `help-echo' property:

        (if (memq (get-text-property (match-beginning 0) 'face)
                  '(font-lock-string-face font-lock-doc-face
                    font-lock-comment-face))
            font-lock-warning-face)

    I don't understand what in Emacs removes this useful help message and why?

It failed for me too, but after I recompiled font-lock.el,
it started working.