What if the language the Human speaks is a language present in Equestria, just not their main language. Example, Japanese/Neighponese, there might be some speakers of it in Equestria, but not a lot. Could that go in this group?

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Wayward Courier by Speven Dillberg have English be identical to 'Zebraven,' Zecora's mother-tongue.

Worked quite well in that story, especially in combo with how magic is close enough to radiation that it can kill humans... and any time the cast wants to understand each other without Zecora around a translation spell is needed.

A small difference, but it does give every bit of two-way dialog this rather nifty 'ticking clock' aspect.