Don't quote nil and t in doc strings

This is as per "Tips for Documentation Strings" in the elisp manual.
For consistency, do the same in diagnostics and comments.

7 files changed, 8 insertions, 8 deletions

diff --git a/lisp/gnus/deuglify.el b/lisp/gnus/deuglify.el
index df54f74e4ef..b2a725b5402 100644
--- a/lisp/gnus/deuglify.el
+++ b/lisp/gnus/deuglify.el
@@ -78,7 +78,7 @@
 ;; `gnus-outlook-deuglify-unwrap-stop-chars'.  Setting this to ".?!"
 ;; inhibits unwrapping if the cited line ends with a full stop,
 ;; question mark or exclamation mark.  Note that this variable
-;; defaults to `nil', triggering a few false positives but generally
+;; defaults to nil, triggering a few false positives but generally
 ;; giving you better results.
 ;;
 ;; Unwrapping works on every level of citation.  Thus you will be able
diff --git a/lisp/gnus/gnus-cus.el b/lisp/gnus/gnus-cus.el
index 9271322f4ab..93b7a1ba635 100644
--- a/lisp/gnus/gnus-cus.el
+++ b/lisp/gnus/gnus-cus.el
@@ -272,7 +272,7 @@ DOC is a documentation string for the parameter.")
                (repeat (list (string :format "%v" :tag "File name"))))
        "Which score files to use when using score to select articles to fetch.
 
-    `nil'
+    nil
          All articles will be scored to zero (0).
 
     `file'
diff --git a/lisp/gnus/gnus-sum.el b/lisp/gnus/gnus-sum.el
index 1d8ad8e6acb..37a707ebe64 100644
--- a/lisp/gnus/gnus-sum.el
+++ b/lisp/gnus/gnus-sum.el
@@ -4376,7 +4376,7 @@ Returns HEADER if it was entered in the DEPENDENCIES.  Returns nil otherwise."
      ;; The last case ignores an existing entry, except it adds any
      ;; additional Xrefs (in case the two articles came from different
      ;; servers.
-     ;; Also sets `header' to `nil' meaning that the `dependencies'
+     ;; Also sets `header' to nil meaning that the `dependencies'
      ;; table was *not* modified.
      (t
       (mail-header-set-xref
diff --git a/lisp/gnus/message.el b/lisp/gnus/message.el
index 8bb0a78a446..9e813e6dfd1 100644
--- a/lisp/gnus/message.el
+++ b/lisp/gnus/message.el
@@ -1123,7 +1123,7 @@ e.g. using `gnus-posting-styles':
 
 (defcustom message-cite-style nil
   "*The overall style to be used when yanking cited text.
-Value is either `nil' (no variable overrides) or a let-style list
+Value is either nil (no variable overrides) or a let-style list
 of pairs (VARIABLE VALUE) that will be bound in
 `message-yank-original' to do the quoting.
 
diff --git a/lisp/gnus/nndoc.el b/lisp/gnus/nndoc.el
index c62697b6939..70d803faf54 100644
--- a/lisp/gnus/nndoc.el
+++ b/lisp/gnus/nndoc.el
@@ -199,7 +199,7 @@ from the document.")
 ;; lines in the body.  For MIME dissections only, ARTICLE-INSERT [5] and
 ;; SUMMARY-INSERT [6] give headers to insert for full article or summary line
 ;; generation, respectively.  Other headers usually follow directly from the
-;; buffer.  Value `nil' means no insert.
+;; buffer.  Value nil means no insert.
 (defvoo nndoc-dissection-alist nil)
 (defvoo nndoc-prepare-body-function nil)
 (defvoo nndoc-generate-head-function nil)
diff --git a/lisp/gnus/nnmaildir.el b/lisp/gnus/nnmaildir.el
index 21fa5b37aa4..da3d5460c2b 100644
--- a/lisp/gnus/nnmaildir.el
+++ b/lisp/gnus/nnmaildir.el
@@ -84,13 +84,13 @@ Some of the FLAGS correspond to Gnus marks.")
 
 (defsubst nnmaildir--mark-to-flag (mark)
   "Find the Maildir flag that corresponds to MARK (an atom).
-Return a character, or `nil' if not found.
+Return a character, or nil if not found.
 See `nnmaildir-flag-mark-mapping'."
   (car (rassq mark nnmaildir-flag-mark-mapping)))
 
 (defsubst nnmaildir--flag-to-mark (flag)
   "Find the Gnus mark that corresponds to FLAG (a character).
-Return an atom, or `nil' if not found.
+Return an atom, or nil if not found.
 See `nnmaildir-flag-mark-mapping'."
   (cdr (assq flag nnmaildir-flag-mark-mapping)))
 
diff --git a/lisp/gnus/rfc2047.el b/lisp/gnus/rfc2047.el
index b2520b26af9..ea558d75a20 100644
--- a/lisp/gnus/rfc2047.el
+++ b/lisp/gnus/rfc2047.el
@@ -1136,7 +1136,7 @@ other than `\"' and `\\' in quoted strings."
 	  ;; `decode-coding-string' in Emacs offers a third optional
 	  ;; arg NOCOPY to avoid consing a new string if the decoding
 	  ;; is "trivial".  Unfortunately it currently doesn't
-	  ;; consider anything else than a `nil' coding system
+	  ;; consider anything else than a nil coding system
 	  ;; trivial.
 	  ;; `rfc2047-decode-string' is called multiple times for each
 	  ;; article during summary buffer generation, and we really