Technically, I think it's supposed to be upper case and that was certainly the norm several years back.
Nowadays, the convention seems to have changed to lower case and certainly that's what most authors use these days, I think. To the extent that if I now see a capital it looks odd to me - whether it's grammatically correct or not. Just because it's now a rarity and something I don't often see.
As far as Archive policy goes - regardless of the technical correctness of either form, whichever that might be - we'll accept either and leave it to the author to choose. All we'd ask is consistency - use one of the other throughout your story and don't switch between the two.
LabRat
