(Does anyone know Mike Northam's current email address?)

In addition to the basic signature instructions in 1.1 above, users of GNUS
should verify that the value of the variable gnus-signature-file points to the
right place.  If you're in emacs, you can do so by evaluating the following
expression:
gnus-signature-file
                   ^ put your cursor here and type C-x C-e

You should see "~/.signature" in the echo area.  If not, edit your
$HOME/.emacs file and add the following:

(setq gnus-signature-file "~/.signature"))

Then load your $HOME/.emacs file or merely restart emacs and the variable
should be set correctly.