Marc S' proposal is, in my humble opinion, very improbable and does not do the topic any justice. The verse simply can't be an interpolation added sometime in the ninth century. That is just precluded by all the evidence. If anything, Altara's suggestion, following Gallez and others, is more probably and has some explanatory scope.
You have the right to disagree with me my friend ; everyone share his opinion.
I read Witzum paper but I am not convinced :
- he put his review in the frame of Abraham/Ishmael building the Ka'aba,
- that allows him not to address one issue in verse 126 so, I am asking you dear Maghraye, what is the city mentionned in that verse ? I cannot really place the context,
- he also seems to link 2:127 and the trial of Abraham by God with the sacrifice of Isaac ; however, to my knowledge, the earliest and the majority of the Quran scholars did recognize that this trial involved Isaac and not Ismael.
But, Allah knows best.