The presence of other languages in shows is an issue that cannot be solved with current #subtitling guidelines.

Viewers can perceive that another language is spoken, but can they identify which one? 1/...

#L3AVT
https://www.youtube.com/watch?v=lo6YNWZBe5k

Sometimes, if viewers know the plot well, they can guess (e.g. from character's origin). But in cases such as #VikingsValhalla, it is not that easy. Characters speak Arabic, Greek and Latin with such a strong English accent that the languages become unrecognizable. 2/...

The presence of the other language might not always be crucial for understanding the plot, serving other functions (setting, verisimilitude).

But what happens when it does? 3/...