The vendor: the one observer who is a person
Every other observer in this catalogue is a machine, a network or an institution. This one is a human being with a memory, a filing habit and a life you cannot see.
The vendor is the observer you deal with on purpose. Your network watches because it carries your traffic. The postal system watches because it moves objects. The vendor learns things because a transaction cannot happen unless you tell them something.
That makes this branch different in two directions at once. In one direction the vendor is weaker than people assume. They see none of your network, none of your device, none of your circuit. In the other direction they are stronger than people assume, because the one fact they do receive is the strongest single fact in the catalogue, and it is handed over deliberately.
A person is not a server
A server does the same thing on a Tuesday that it did on a Friday. It applies a retention policy because somebody configured one. It does not get bored, does not gossip, does not keep a second copy of something because the first copy was awkward to search.
A person does all of those things. That is not a claim about any particular vendor. It is a claim about what it means for the reader to be human, and it holds however careful that person is.
Memory has no schema
A database can only join two records if somebody built a field to join them on. A person recognises. They read a message and think that they have seen that phrasing before, or that turn of politeness, or that particular way of asking about timing. Nothing was indexed. No query was run. The link was made anyway.
Memory fails in the other direction too. A vendor may forget an exchange entirely, or attach a memory to the wrong account and act on a connection that does not exist. An observer who is sometimes wrong is still an observer.
Notes are kept for the note taker
Whatever record a vendor keeps, they keep it because it is convenient for them. A spreadsheet, a text file, a notebook, a printed sheet, a name in a phone. The organising principle is their workflow, not your exposure.
This has one blunt consequence. Anything deleted inside the platform is deleted inside the platform. A copy a person made outside it is outside your reach and outside the platform's reach as well. The equivalent problem on your own side is covered in what lands on the disk, and the reasoning is identical: a copy is a copy wherever it lives.
An account is not always one person
A vendor account can be operated by more than one person at a time, and it can pass to a different person over time. Staff, a partner, a shift handover, an account sold or inherited. None of this is announced. The interface shows one name and one history whether or not the human behind it changed in March.
So when this branch says the vendor learns something, read it as the account learns it. The set of people standing behind that account at the moment you write is unknown to you, is not fixed, and is not something the platform can tell you.
Their security is invisible to you
You cannot see the vendor's machine, their disk, how they store keys, whether the device is shared, whether anything is written down beside it, or which jurisdiction any of it sits in. You cannot check a claim they make about any of it, because there is no way to verify such a claim from the buyer side of a conversation. This site does not publish assessments of individual vendors and will not.
Hold this as an unknown rather than as a risk you have measured. Whatever you supply sits on somebody else's equipment under conditions you will never inspect. That is a description of the arrangement, not an accusation about anyone in it.
Everything they know, you handed over
The vendor learns nothing by watching a wire. They have no vantage point on your connection at all. Every fact they hold about you arrived because you typed it, chose it or clicked it. That is the reverse of the Tor branch, where observers collect things you never offered.
Mostly you had no choice. A delivery cannot happen without a place. That single unavoidable disclosure is the subject of the address you hand over, which is the central page of this branch and probably of the whole catalogue.
Two observers watch the same six actions
Every action in this branch happens on a platform, so the market server sees it as well. Ordering, messaging and disputing are all two observer events by construction. Where the two see different things, the card says so rather than repeating the server side of the story.
The six cards in this branch
Each card takes one action, names who sees it, and spends as much space on what is not learned as on what is. Start with the address card if you only read one.
The full set of forty two actions across all seven observers is in the catalogue, and the observers themselves are compared side by side on the observers page.
Questions that come up
Does the vendor see my IP address or my location?
No. The vendor has no view of your network at all. Anything they know about where you are came from something you wrote, most often the delivery address itself.
Can I tell whether a vendor keeps records?
No, and nothing on the platform reports it. You can see what you sent. You cannot see what was copied, filed or remembered on the other side.