Frequently when I see ancient texts translated from languages like Hebrew, personal pronouns are rendered as "thou" or "thy" or other archaic forms. It might make sense for some religious texts as their original translations might have been done when those pronouns were still in common use, but it still seems to be done every now and then. Why?
Edit: as an example "O Osiris, everything which is hateful in Unas hath been carried away for thee; for that which was uttered in his name of evil hath Thoth come, and he hath carried it away to Osiris. I have brought that which was spoken in the name of Unas of evil, and have placed it in the palm of thy hand. The SA shall not be separated from thee, and thou shalt not be separated from it." From pyramid texts translated by E. A. Wallis Budge [1909].
The formal/informal thing makes a lot of sense. We don't normally differentiate in modern English. What are some of your opinions about doing it for aesthetic purposes?
Reasons can vary, you would have to give a specific example of a text and its translation in order to gauge why a translator made the choice to employ what are now archaic forms. If you would care to provide a specific example perhaps I or another could give you a more definite reason.
Without a specific example, reasons might include:
There could be other reasons too.
Thanks for editing and providing an example text. Remember that in 1909 English usage would have more commonly understood thou/thee, but more importantly the KJV was still in widespread usage, so that religious language in particular held on to such usage. I would suggest that a translation from this time, even of a non-Christian religious text, would imitate KJV language in order to indicate religious-type speech.
Particularly when dealing with a formal exchange the translator may want to keep some shades of reverence that would otherwise be lost.