Trust
What this account holds, what it does not, and who to tell when something is wrong.
What an hm account is
An account is an identity and the organisation it belongs to: an email address, a password held by the authentication service, the people you share an organisation with, and a short list of preferences that follow you between machines.
That is the whole of it. Your Works — what you are building, who is working on what, and everything inside them — are folders on your own machines. They are made and read by the hm binary, they are never uploaded here, and no page on this surface can reach them.
How the pieces are split
Three services stand behind this address, and the split is deliberate: one is the authority for who you are, one for who you belong to, and this one — the pages you are reading — is a client of both. It stores nothing itself. It holds no password, no signing key, and no database.