BuddyPress.org

I haven’t looked at this at all but I’m just guessing that you might want to try referencing the newer functions whose filters use different ways to set their values:

add_filter('bp_get_the_topic_post_content', 'my_smilies_fixurl', 30);

add_filter('bp_get_wire_post_content', 'my_smilies_fixurl', 10);

I have no idea if this will work.