Tales of Destiny R is a result of timeline changes.Tales of Destiny and its remake have some noticable differences, from minor things Stahn and Lion no longer using a shield, to major things like Lion dying a hero. This is because in Tales of Destiny 2, all of the influences to the time line done by Elraine, Fortuna, Barbaratos and Kyle's group changed it to the point that Fortuna's death wasn't enough to completely reset it.
The personality in Swordian Berselius isn't Karell- it's Harold.Berselius never actually speaks as itself, just Miktran, who was possessing it. Berselius has a gold core. Most of the Swordians have silver cores, and the only other one with a gold core is Atwight, which used a woman's personality. Karell was the one who originally wielded Berselius, but it was made by his eccentric sister, Harold, who regularly does things simply because she thinks they'd be entertaining. It seems reasonable that she'd put her own personality into her brother's Swordian as a prank.