Hello I don't know if it's the right place to submit a diff.
The man page X(7) refers to xdm(1) in "SEE ALSO". I also found that the first line of the file is a comment with a character 't' alone. Index: X.man =================================================================== RCS file: /cvs/xenocara/doc/xorg-docs/man/X.man,v retrieving revision 1.4 diff -u -p -r1.4 X.man --- X.man 30 Aug 2015 13:32:02 -0000 1.4 +++ X.man 14 Mar 2018 17:43:15 -0000 @@ -1,4 +1,3 @@ -.\" t .\" .\" Copyright (c) 1994, 2004 The Open Group .\" Copyright \(co 2000 The XFree86 Project, Inc. @@ -1217,7 +1216,6 @@ the appropriate instance name can be pla .BR xclock (__appmansuffix__), .BR xcmsdb (__appmansuffix__), .BR xconsole (__appmansuffix__), -.BR xdm (__appmansuffix__), .BR xdpyinfo (__appmansuffix__), .BR xfd (__appmansuffix__), .BR xfs (__appmansuffix__),
