Adopt Frank's version, in part

l3kernel/l3tl.dtx

@@ -330,12 +330,13 @@
 %     \cs{tl_if_novalue_p:n} \Arg{token list}
 %     \cs{tl_if_novalue:nTF} \Arg{token list} \Arg{true code} \Arg{false code}
 %   \end{syntax}
-%   Tests if the \meta{token list} is exactly equal to the content of special
-%   \cs{c_novalue_tl} marker, hence it is functionally the same as
-%   \begin{quote}
-%     \cs{tl_if_eq:NnTF} \cs{c_novalue_tl} \Arg{token list} \Arg{true code} \Arg{false code}
-%   \end{quote}
-%   but expandable. This function is intended to allow construction
+%   Tests if the \meta{token list} and the special \cs{c_novalue_tl} marker
+%   contain the same list of tokens, both in respect of character codes and
+%   category codes. This means that
+%   \cs{exp_args:No} \cs{tl_if_novalue:nTF} \{ \cs{c_novalue_tl} \} is 
+%   logically \texttt{true} but \cs{tl_if_novalue:nTF} \{  \cs{c_novalue_tl} \}
+%   is logically \texttt{false}.
+%   This function is intended to allow construction
 %   of flexible document interface structures in which missing optional
 %   arguments are detected.
 % \end{function}