Making changes to /usr/share/X11/locale/en_US.UTF-8/Compose was, at least for some time, the only way to make keyboard composition work in Ubuntu, as ~/.XCompose didn't work anymore, and creating a custom keyboard layout from scratch was not an option (my XCompose contains key compositions for almost the entire non-JCK UniCode character set in XCompose-coding).
Making changes to /usr/share/ X11/locale/ en_US.UTF- 8/Compose was, at least for some time, the only way to make keyboard composition work in Ubuntu, as ~/.XCompose didn't work anymore, and creating a custom keyboard layout from scratch was not an option (my XCompose contains key compositions for almost the entire non-JCK UniCode character set in XCompose-coding).