Why in dired+ mode some text is strikethrough?

Question

Windows 10, Emacs 26.1, Dired+ (download from here https://www.emacswiki.org/emacs/download/dired%2b.el)

Open some directory:

Here result:

Why some text is strikethrough?

Answer 1

They are displayed in the diredp-omit-file-name face defined in the very same file:

(defface diredp-omit-file-name
  (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-through "#AAAAAAAAAAAA"))) ; ~ light gray
    '((((background dark)) (:foreground "#C29D6F156F15")) ; ~ salmon
      (t                   (:foreground "#00006DE06DE0")))) ; ~ dark cyan
  "*Face used for files whose names will be omitted in `dired-omit-mode'.
This means file names that match regexp `diredp-omit-files-regexp'.
\(File names matching `dired-omit-extensions' are highlighted with face
`diredp-ignored-file-name' instead.)"

If you don't like the current appearance of the face, you can customize it using customize-face.

Answer 2

Just remove the strike-throughs in lines 3839-3842 of dired+.el, to give

(defface diredp-omit-file-name ;;
 (if (assq :inherit custom-face-attributes) ; Emacs 22+
  '((((background dark)) (:inherit diredp-ignored-file-name))
    (t                   (:inherit diredp-ignored-file-name)))

Either rename the file or make a note of the change so you're not caught out in an update.