Interesting observations in Mosiah today. From Mosiah 1, the following seems self evident: Even though they’d been together for at least a generation, there are two distinct peoples. You see that in Mosiah 1:10.
Mosiah 1:10 … My son, I would that ye should make a proclamation throughout all this land among all this people, or the people of Zarahemla, and the people of Mosiah who dwell in the land, that thereby they may be gathered together….
There are also multiple languages. Why you ask? Because Benjamin taught his sons “the language of their fathers.” Well wouldn’t that be obvious? Why mention it if it were normal? Unless it’s not. Since Mormon made mention of it, it seems safe to assume there was another language which they spoke aside from the "language of their fathers." Reading between the lines, it seems there could have been as many as four languages for them to learn, not counting what the Lamanites spoke.
1. There’s the unmentioned language which everyone speaks. (Else why make mention of teaching them any language at all.)
2. There’s the language of their fathers.
3. From verse four, there’s Egyptian, otherwise how do they read the Brass Plates.
4. Then there’s the language of the people of Zarahemla, which at one time was probably Hebrew just like what Lehi and his family spoke when they fled Jerusalem. It had evolved over the centuries too. In Omni we read that the people of Zarahemla couldn’t be understood by the Nephites because their language had diverged so far from what the Nephite’s spoke.
Omni 17 "And at the time that Mosiah discovered them, … their language had become corrupted; and they had brought no records with them; … and Mosiah, nor the people of Mosiah, could understand them."
Who’s to say the Nephite language hadn’t undergone its own changes too? Who knows what the Lamanites speak by that time: it had been hundreds of years since they read any Nephite record. Yet the interaction between Zenniff and King Laman show they could still understand each other.
Why is this important? It's not really. I just find it interesting for it shows me there's a lot more to the Nephite and Lamanite cultures than a casual read will show.