Has anyone besides me ever wondered why the words
Muslim and Islam are left untranslated in some instances 
Because the author / translator thinks that "Muslim" and "Islam" are indeed "Identity".
In the same manner as Allah are left untranslated, it's yet another persona / identity.
Yet translating the words might cause issues as well. a good case study for this happened with Jesus story / Gospel. Translated into greek and then latin and then english we found weird words such as "Son of Man", "Father in Heaven", "Son Of God".
Greek, Latin and English language were forged within natively pagan tradition, well so does Arabic language for that matter. The paganistic people see that God as if it is a human king and there are many of them, each God fighting other Gods, hating each others and often at war with each others in an effort of trying to be an ultimate superior God. The God of all the Gods.
Each God then recruited human as followers by creating a religion, and the God get angry if He lose a followers especially if the human joining other religion of other rivaling Gods. As thus such deed is declared as "unforgiven sin" the punishment is death. Such punishment is necessary to strike fear into the heart of the God's followers thus nobody dare to leave His religion and join other rivaling God's religion.
Back to the case study of Jesus story.
Encountering "Son Of God" and "Father", the conception of pagans / polytheists is a human like deity who had a descendant thus also another God called the son of that God called the Father. Well then there's two God already, the God and his son which also a God, no longer one.. Just like Zeus and Hercules..
The confusion of introducing monotheism to natively polytheist society is many converted polytheist still view "God" with polytheist lenses, the lenses which they're familiar with, the lenses and mindset on which the language being forged . They don't understand on WHY there could only be ONE God in the first place.
They believe that there is only ONE God just because God said so.
And if they don't believe that there is only one God, that God will be angry and will punish them.
Just like the good ol' polytheistic Gods used to do....