[@KatherinWinter]
It's hard to explain the mechanics of it, but for one thing erasing or altering a single memory doesn't actually impact a character's personality to any noticeable degree.

To truly change a person, you would need to remove an entire lifetime's worth of memories; every single key moment in their life which is connected to a removed memory would also have to be extracted to break the sequence and cause a change.

Example: As a kid, you're afraid of the dark. Maybe one of your parents puts a fancy looking night light in your room and tells you it's a magic light that will chase the monsters away. That nightlight remains in your bedroom for, say, five years. Even if the memory of the light being put in were to be removed, the memories of not being afraid because the light was there will remain.

Like a bracelet made of colorful beads on a string, even if you take one of the beads out the string that holds the thing together is still there, you've simply created a gap in the decorations on the bracelet. To destroy the bracelet, you'd have to cut the string and remove ALL of the beads; not just remove one or two of them.

On the subject of creating fake memories: The false memoriesi mplanted by Djinn are what they call hollows; devoid of any emotional energy and unable to replace a real memory within the overall sequence; he can glue it on to hide the gap between two memories, but the underlying connections between memories is impossible to alter.
To return to the bracelet metaphor: If you remove, say, a bright red bead with gold glitter in the plastic, he wouldn't be able to replace it with another red glittery bead. The replacement would be plain, clear plastic; and more importantly, the string that ties it all together still remains unbroken.