I was wondering why didn't they make Desmond retain his Ancestor's Foreign Languages? I mean Desmond retain his Assassin Ancestor's assassination skills but not their language? Did they mention it why they didn't do it?
Rebecca, and Abstergo installs a Translation Software for the viewers watching it. But for the Animus user it should have them remember everything from skills, memories, to foreign language. For example when Desmond is inside the Animus reliving his ancestor's memories he can understand the people who speaks a foreign language but he doesn't understand why he can understand them and someone explains it to him because his ancestor can speak and understand the language. What I'm trying to say is that the Translation Software should be for the viewers who wish the watch it if they aren't using the Animus but watching it from a computer video and for the Animus User that's not the case because they are reliving as their ancestor and through the Bleeding effect they can speak it.
They could make Desmond speak foreign language fluently when he talks to Lucy, Rebecca, and Shaun. They could also make him occasionally speak some foreign language like when Ezio speaks English but he speaks some Italian. His friends can joke, comment, etc his ability to speak a foreign language.
The only Animus Subject that can speak a Foreign Language is Daniel Cross and he's speaking it subconsciously.