man page and usage: -D

Mention the changed character name that happens when running in wizard
mode.

dat/usagehlp

@@ -1,6 +1,6 @@
 This is a terse description of nethack's command line arguments.
-It is oriented toward UNIX (including descendants such as linux and
-macOS) and might not be accurate for other platforms.
+It is oriented toward UNIX (including descendants such as linux and macOS)
+and might not be accurate for other platforms.
 
 When starting play, if there is a save file for the chosen character name
 then it will be restored, otherwise a new game using that name will begin.
@@ -17,7 +17,8 @@ nethack -u character-name [-X or -D]
        -X must be uppercase; character starts with a wand of wishing and
        player may opt to be life-saved and keep going if character dies;
   '-D' run in debug mode also known as wizard mode; -D must be uppercase;
-       if player is not allowed then nethack will switch to -X.
+       if player is not allowed then nethack will switch to -X; if player
+       is allowed, character name will be changed to "wizard".
 
   A character name may have a suffix specifying any or all of role, race,
   gender, and alignment such as -u Conan-Bar-Hum-Mal-Neu or -u Tim-Wiz.

doc/nethack.6

@@ -288,10 +288,10 @@ The
 option will start the game in a special non-scoring discovery mode
 (also known as explore mode).
 .B \-D
-will start the game in debug mode (also known as wizard mode),
-if the player is allowed, otherwise if will switch to
-.BR \-X
-instead.
+will start the game in debug mode (also known as wizard mode) after
+changing the character name to \(lqwizard\(rq, if the player is allowed.
+Otherwise it will switch to
+.BR \-X .
 Control of who is allowed to use debug mode is done via the
 .RI "\(lq" WIZARDS= "\(rq line in nethack's " sysconf " file."
 .PP