Some talk on the Discord got me thinking about how I've been handling the subject of reincarnation and past lives. Rather than fully explaining it there and letting it go lost, it makes more sense to throw it here and have it be threadmarked. So without further ado...
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Digimon are highly malleable creatures, beings that change massively over their course of their lives. The root cause of these changes can be attributed to one main aspects. Foreign interactions, be it taking in data or forming a personality due to social stimuli. These influence how digimons develop both physically and mentally, which determines how they later digivolve.
After being deleted, the *core* being of the digimon is reincarnated, saving the very basics of their personality and occasionally even bringing hints of memory along. Despite that, from one life to the next a digimon can change dramatically, going through entirely different evolutions and living extremely different lives.
That brings the question, are they in fact the same digimon whom perished? Well, yes and no. There will nearly always be hints of whom the digimon was before, special personality traits, verbal tics and even the rare physical trait. Indeed, the starting talents and stats of a mon are even based off their past life. However what differences occur in their next life will without exception produce an undeniably changed digimon.
A villain can become a hero, a ruler can become a tyrant, a pacifist can become a great warrior and vice versa. Changes that extreme are generally rare over the course of a single cycle, but over multiple incarnations anything is possible.
Said changes are not purely mental either, they go down to the very core itself. Cores themselves grow and change from the body's data which in turn takes foreign material, be it loading or eating. And of course, the biggest changes to a core come from evolution. Each digimon has a differently structured core depending on their current and previous forms. Two Ultimates of the same species can even have radically different cores depending on their champion and rookie evolutions.
Meaning that the core of a mon can be unrecognizable from one life to the next. Which makes finding a reincarnated digimon nigh impossible past a certain point.
It's why Pit wasn't instantly outed as Daemon the first time he stepped onto a Host Scanner. As for most physical intents and purposes he isn't him.
As an ending note, If a digimon can be reborn in a similar environment to its past existence, they are likely to turn out very similar.