-.Sh COMPATIBILITY
-This section mentions some areas of questionable portability between
-implementations of the
-.Nm
-language.
-More incompatibilities exist.
-.Pp
-.Bl -dash -compact
-.It
-Do not depend on
-.Sx \&SH
-or
-.Sx \&SS
-to close out a literal context opened with
-.Sx \&nf .
-This behaviour may not be portable.
-.It
-troff suppresses a newline before
-.Sq \(aq
-macro output; in mandoc, it is an alias for the standard
-.Sq \&.
-control character.
-.It
-In page header lines, GNU troff versions up to and including 1.21
-only print
-.Ar volume
-names explicitly specified in the
-.Sx \&TH
-macro; mandoc and newer groff print the default volume name
-corresponding to the
-.Ar section
-number when no
-.Ar volume
-is given, like in
-.Xr mdoc 7 .
-.El
-.Pp
-The
-.Sx EE ,
-.Sx EX ,
-.Sx OP ,
-.Sx UE ,
-and
-.Sx UR
-macros are part of the GNU extended
-.Nm
-macro set, and may not be portable to non-GNU troff implementations.