I don't really get what you're objecting to, though? The only "headcanon" I've mentioned is actually just an opinion whether the personalities from the past and the present are the same or not, from what little is showed in the canons about the past I don't really see many differences except for Usagi and Kunzite (live action only) and it's based on that where I said they had the same personalities. You can disagree but I don't think you can deny that what we are shown of the past lives of most of the characters differs from the present ones except in the cases I've mentioned.

Regarding the word used in the original Japanese, back in my first tag about this I said: I bold the reborn part because it's not the same as a reincarnation as far as I understand it. And I hold my ground on that, for me, it's more a rebirth than a reincarnation though really, at the end of the day, whether they were all reborn or reincarnated the situation in general stays the same. As you yourself have said reincarnation means that you have the same soul, anything else gained from it is "optional", being reborn also means that they have the same soul but it's strictly that without any optional extras.