The exploit:
Barter something cheap as a gift with someone.
Get 1 charm level.
Get out of the conversation back to the world map.
Save -> Load the game you just saved
You can now barter again with the exact same person.
Pick that cheap thing you just gave this person and choose auto-barter so to pay in exact gold.
Get 1 charm level.
Save -> Load
Repeat
Every cycle gets you 2 charm levels out of loading the game 2 times.
The game does not save that you recently bartered.
Barter something cheap as a gift with someone.
Get 1 charm level.
Get out of the conversation back to the world map.
Save -> Load the game you just saved
You can now barter again with the exact same person.
Pick that cheap thing you just gave this person and choose auto-barter so to pay in exact gold.
Get 1 charm level.
Save -> Load
Repeat
Every cycle gets you 2 charm levels out of loading the game 2 times.
The game does not save that you recently bartered.