I had proposed the following suggestion in the xserver-xfree86 package
  (bug #90030):

  To which Branden replied:

  I would suggest working with Branden Robinson <branden@debian.org> to
  hammer out the API details. In most cases, the choices are few, and
  are fully described in the debconf screen. In other cases, the choices
  are many, and therefore each choice cannot be described at all on the
  debconf screen.

  In my particular case, a single Help button would have been good so
  that I could have searched for my video card (G200) to discover that
  the "mga" driver was appropriate for me (an implementation of "$PAGER
  $file" would have sufficed nicely since it would have provided the
  search capability needed).

  In this case, having individual Help buttons next to each choice (as
  in the Linux kernel configuration) would not have been helpful
  (indeed, extremely tedious!). Nonetheless, I can see that having
  individual help buttons may be useful--it could replace the inline
  descriptions of today.

Bill Wohler wrote:

Debconf's extended descriptions are intended to be medium-sized help
texts. It is nearly impossible to add a help button to some debconf
frontends, such as the dialog frontend (dialog has no provision for help
buttons).  In other frontends, such as the gnome frontend, the extended
descriptions are indeed visible only by kernel-config-esque help
buttons.

Implementing some system in debconf for more extensive help texts is
unlikely to happen any time soon, if at all.