- The question is clearly about the history of grammatical development in English, specifically about the grammatical use of 'I', and so the question is clearly within the topical scope of ELU.
- Even supposing I've overlooked some defensible argument that puts the question outside that scope, nobody who voted to close saw fit to comment on how the question falls outside the scope of ELU, so the OP has no route forward for editing to re-open the question.
As "defensible argument" I don't include arguments that fly in the face of the long-established and still extant primary definition of 'grammar':
That department of the study of a language which deals with its inflexional forms or other means of indicating the relations of words in the sentence, and with the rules for employing these in accordance with established usage; ....
["grammar, n.". OED Online. September 2016. Oxford University Press. http://www.oed.com/view/Entry/80574?rskey=2ACPm8&result=1&isAdvanced=false (accessed October 10, 2016). Emphasis mine.]