Lars Ingebrigtsen <larsi@gnus.org> writes:

> After the patch, it says "Hide-fill-column", which doesn't exist either,
> but which is basically the same bug -- which is that there's an
> invisible string "Hide" before the "Fill Column".
>
> Hm...  Oh!  If I move point into "Fill Column", then it guesses
> correctly, but if point is at the "F", then it includes the invisible
> "Hide".

You are right.  So this patch didn't break `C-h S' at all, it just made
the bug a lot more visible.

Anyway, my lightly testing shows that perhaps relying on the :regexp and
not providing :parse-rule could be enough.