Your account
An account is a username and a password, nothing more. The username is 3 to 15 letters, digits or _; make it up, do not use your name. The password is 8 to 72 characters. Shelf never asks for an e-mail address, a phone number or a real card.
Signing in gives you a token that is valid for 8 hours. The Account page shows it for API tools; send it as Authorization: Bearer followed by the token.
Your data is yours only
Your cart, your orders, your payment attempts and the products you create are visible only to you. No other account can open them, and Ask Shelf answers only about orders of the account you are signed in with.
Reset and delete
"Reset my data" on the Account page, or "Reset the shop" at the top of every page, deletes your cart, orders, payment attempts and products. The account stays. "Delete account" deletes the account with everything in it. Accounts that nobody uses for 14 days are deleted with their data.