If this command acts on the entire buffer (i.e. if called
interactively with the mark inactive, or called from Lisp with
-@var{end} nil), it also deletes all trailing lines at the end of the
+@var{end} @code{nil}), it also deletes all trailing lines at the end of the
buffer if the variable @code{delete-trailing-lines} is non-@code{nil}.
@end deffn
(@pxref{Special Properties}), such as a face name or an anonymous face
(@pxref{Faces}).
-If any text in the region already has a non-nil @code{face} property,
+If any text in the region already has a non-@code{nil} @code{face} property,
those face(s) are retained. This function sets the @code{face}
property to a list of faces, with @var{face} as the first element (by
default) and the pre-existing faces as the remaining elements. If the