If you set the language to a not-supported one (I used the installer from mattn.ninex.info and ufo-ai automatically selected my locale which is nl-NL), research texts show up as their filenames (e.g. 'laser-pre.txt') instead of picking the english file content as default. - my ufoai version is 2.1.1, beta test installer.
When I symlinked the en directory in i18n as nl, i got the english texts, so the i18n directory apparently was found.