There's an occasional trope in fiction where a character who's done something really bad and reforms is said by themselves or another character to be "not the same person who did those things", and therefore absolved from guilt even if they haven't made up for it yet.

This is probably one of the less harmful minor ideas, but it's still wrong. They are the same person and repenting doesn't automatically clear you of past guilt, just makes it wrong for others to enact punitive retribution. Restitution is still owed. I hope someone who reads this will shake their head at the trope the next time they see it.