and in the same vein there’s the premise that all these works are just translations of manuscripts he found as part of his work as a linguist. so in canon everything we know comes from a translation of a copy of a single source with limited information
the Tolkien legendarium is a lot more loose than most people think. it’s got a reputation for a high degree of specificity and detail, but that’s more true for some things than others, and sometimes those details are contradictory between different versions of the same story throughout the editing process, with no clear indication of which one should be considered canonical
I don’t see how representing foreign dialogue with foreign text subverts the author’s intent. sure, they may not intend for their general audience to understand, but they still won’t. and they must have known, and maybe even intended, that a certain part of the audience would understand, and if the foreign text were shown, they could
I’ve definitely seen movies where common Spanish words or phrases that an anglophone audience would be expected to understand are transcribed as simply “[speaking Spanish]”
e.g. “that hombre is loco” becomes “that [speaking Spanish] is [speaking Spanish]”
I know this is a joke question, but there is an answer, and it’s Eärendil the Mariner