Factual error: The Pakistan Army uses British-style rank insignia with the crown replaced with The Star and crescent of Pakistan. The ISI officers are all wearing another badge instead of The Star and crescent. They are also wearing black gorget (collar) patches, whereas they should be wearing scarlet. Lt Col Khan and a number of other more junior officers should not be wearing gorget patches at all, as they are restricted to full colonels and above. ISI officers do not have a separate uniform; they wear ordinary military uniform if they are entitled to it.
Factual error: The man who approaches Carrie in the bar identifies himself as a 'lieutenant JG', and the pilot who bombed the wedding party in the farmhouse. However, it was F-15s that dropped the bombs on the farmhouse, making them US Air Force aircraft. The USAF rank structure doesn't include the 'JG' rank- that's a US Navy rank.
Factual error: The Pakistan Air Force officer in the airport is listed in the credits as 'PAF Lieutenant' and is wearing the two pips of an army lieutenant. In fact, the PAF still uses RAF-style ranks, so he should be a Flying Officer, and the PAF also uses distinctive eight-pointed stars instead of pips.
Chosen answer: Everyone else calls him Brody or Sgt. Brody, and it probably became habit to her.
The_Iceman
Can't get the source but I read that even the Producer responded to that. Stating that it was common practise for a military wife living in a military complex as everybody refers to their husband by their last name.