Yoooooo okay I realized something. So we know that shopkeepers can’t be attacked. It isn’t a game function; it’s literally not possible.
When you threaten Gerson, you get:
Shopkeepers/NPCs that sell items are invulnerable to attack due to an in-universe rule that you can’t initiate a fight with anyone who is actively selling something. I say actively because technically you have the option to sell items all the time at different shops (although not every shopkeeper will agree to buy), but monsters will still attack you and bosses can still pull you into a fight. If you’re smart, like Gerson, you can use this weird mechanic to keep yourself safe and alive. You can avoid hostile encounters, and thus damage/death, by becoming a peddler.
And who do we know in this game that a) has dangerously low HP, b) keeps a tight lid on powers that could otherwise be used to protect themselves, and c) is constantly found selling things?
Sans is literally keeping himself alive by selling random stuff.
Bootsrcool 