To my eyes, it looks really good.  A marked improvement.

Here is the diff (make sure to rm lisp/help.elc before testing):

diff --git a/lisp/faces.el b/lisp/faces.el
index 9ec20c4298..ee805ede8a 100644
--- a/lisp/faces.el
+++ b/lisp/faces.el
@@ -2883,13 +2883,17 @@ help-key-binding
      ;; making the characters wider, which then would cause unpleasant
      ;; horizontal shifts of the cursor during C-n/C-p movement
      ;; through a line with this face.
-     :box (:line-width (-1 . -1) :color "grey80"))
+     :box (:line-width (-1 . -1) :color "grey80")
+     :inherit fixed-pitch)
     (((class color) (min-colors 88) (background dark))
      :background "grey19" :foreground "LightBlue"
-     :box (:line-width (-1 . -1) :color "grey35"))
-    (((class color grayscale) (background light)) :background "grey90")
-    (((class color grayscale) (background dark)) :background "grey25")
-    (t :background "grey90"))
+     :box (:line-width (-1 . -1) :color "grey35")
+     :inherit fixed-pitch)
+    (((class color grayscale) (background light)) :background "grey90"
+     :inherit fixed-pitch)
+    (((class color grayscale) (background dark)) :background "grey25"
+     :inherit fixed-pitch)
+    (t :background "grey90" :inherit fixed-pitch))
   "Face for keybindings in *Help* buffers.
 
 This face is added by `substitute-command-keys', which see.
diff --git a/lisp/help-macro.el b/lisp/help-macro.el
index 1fa9d82afd..8eba7b7cda 100644
--- a/lisp/help-macro.el
+++ b/lisp/help-macro.el
@@ -140,6 +140,7 @@ make-help-screen
                    (insert (substitute-command-keys help-screen)))
                  (let ((minor-mode-map-alist new-minor-mode-map-alist))
                    (help-mode)
+                   (variable-pitch-mode)
                    (setq new-minor-mode-map-alist minor-mode-map-alist))
                  (goto-char (point-min))
                  (while (or (memq char (append help-event-list