@osuccess, @ofail, and @odrop messages may contain %-substitutions, which evaluate to gender-specific pronouns if the player's sex is set. They are:

%a	(absolute)	Name's, his, hers, its
%s	(subjective)	Name, he, she, it
%o	(objective)	Name, him, her, it
%p	(possessive)	Name's, his, her, its
%r	(reflexive)	Name, himself, herself, itself
%n	(player's name)	Name

Capitalized pronouns are also available with %A, %S, %O, %P, and %R. If you need a '%', use %%.