We don't have a tasteful rule, do we?
Are they sure it's not the other way around? That the language has eroded to a strange mix of guttural sounds and now they use English in order to understand each other?
What about an academic context?In the right context it would be totally acceptable; not archaic at all.
That's nice, but I'm really more interested in the actual perception, not the dictionary definition.Neither Collins nor Merriam-Webster lists this phrase as 'archaic'.