They are displayed in the diredp-omit-file-name face defined in the very same file:
(if (assq :inherit custom-face-attributes) ; Emacs 22+
'((((background dark)) (:inherit diredp-ignored-file-name :strike-through "#555555555555")) ; ~ dark gray
(t (:inherit diredp-ignored-file-name :strike-...
If you change "package" to "^package.*" I think it will match every line that starts with package to the end of the line. I don't know enough about go to know if that is always the right thing to do here.
Just add this, after the defface, to define a variable of the same name, whose value is the face symbol:
(defvar my-r-face 'my-r-face
"Variable for face `my-r-face'.)
font-lock-defaults in the case of just (pgn-highlights) defines font-lock-keywords as the list that is the value of variable pgn-highlights.
The doc for font-lock-keywords tells you about ...
In addition to Adam Michael Wood and lawlist:
C-u C-x = - good way to get information about font symbol
In appered buffer you should follow that paragraph: There are text properties here: and visit highlighted link. This way can help you look through font inheritance.
You can get clear that Mardown Code Face inherits Emacs system fixed-pitch root-font.