Chat is where the people in a workspace talk. A thread can be everyone in the workspace, one other person, or a few of you. It works the way the rest of The Margin does: a message typed on a train appears when the tunnel ends, and the wall display can show the household thread with no network at all.
Who can be in a thread
Anyone in your workspace, which includes the household: a child with a profile and no email is a full member, and the kiosk lets them read and reply as themselves. Beyond your workspaces, people you are connected to. Nobody else, on purpose. A thread that could reach a stranger by a guessed email would be a nuisance, and the rest of the app refuses to be one.
One other person with no title makes a direct thread, and two people have exactly one of those between them, whoever started it.
Hearing about it
You are told once when a thread you have not read has something new, and not again until you read it, so a busy thread does not buzz a phone forty times. Mute a thread to hear nothing from it.
Threads about a thing
A thread can be about something: a record of money owed, a chore, a plan. Where a record offers Discuss, the thread it opens is that record's, and the assistant can find it by asking about the record.
Someone not on Margin
They have no account to address, and the honest thing is to say so. Any thread can be downloaded as a plain transcript to send them.
Your assistant
Ask it what someone said, or tell it to let the family know something, and it reads or writes in the thread as you. It only ever sees threads you are in.