A quote is an extract from your own manuscript, captured and approved by you. Quotes are shared either through the social queue to a connected account, or through the system share sheet on your device.
What can accompany a quote
Attribution to the book title, a buy link, and an image. Attribution is drawn from the book rather than typed, so it cannot disagree with the book it came from. A buy link cannot be selected until the book actually has one, which prevents a post promising a link that does not exist.
Sharing outside the queue
The system share sheet receives the quote and the book it came from, and deliberately no URL. Nothing about a manuscript in progress is public, and a link to a page that shows a sign-in screen is worse than no link at all. Closing the share sheet without sharing is not treated as a failure.
Publishing to a connected account
Quotes queued for a connected account are covered on the social queue page, including how a credential is stored, what happens when a post fails, and how to end access.