Will be good idea to introduce gender switch (male/female) in user preferences.
It is great for Slavic languages (and most likely for other languages too) localization. For example in Russian user namespace should display "Участник" for male and "Участница" for female. For user talk: "Обсуждение_участника" and "Обсуждение_участницы" correspondingly.
At least user and user talk namespaces should be affected with default signature. If database workload will be not too big, special pages (recent changes, page lists, etc) should be improved too.
See also bug 12924.