Monte (the card game) is an English word, so the italics call attention to possible double meanings here. Since Decoud's letter is presumably in French, we could read this as the untranslated French verb monte, meaning "to climb," or "rise," implying that Nostromo's bad luck at social climbing has kept him poor. Even more interestingly, monte is Spanish for "mountain," giving the line a symbolic meaning, since mountains symbolize the ideal. In this case it is the People's bad luck at the "game" of great ideals that keeps them poor.