I kind of feel that your first contact policies should impact how you translate their language, and whether you even properly establish communications. Even if you are capable of communicating, I feel like nations like fanatic purifiers should basically ignore all attempts to communicate, acting as though they were still engaging in a first contact war even though you have been aware of each other for years.
It would also be interesting if the degree of difference in traits, species type, and ethos could impact how long it takes to translate each other's language -- while groups similar (like Star Trek Humans / Vulcans) would find it easy to communicate, others would be locked in a first contact situation, even a first contact war, for a very long time (think Ender's Game human / formic wars, where the communications barrier ultimately leads to a first contact war ending with xenocide). The more alien they are, the harder it is to even speak to each other, let alone find common ground.