One key or several
The same shape as reusing a name, with the difference that a key makes the link provable rather than merely likely.
A fresh key per identity
- What you gain
- No cryptographic link between this and anything else. Nothing to correlate, now or later.
- What you give up
- You cannot prove continuity, which is a real loss for a vendor and close to irrelevant for a buyer.
- Suits
- Every buyer.
One key everywhere
- What you gain
- Provable continuity across platforms, which lets an established trader carry standing with them.
- What you give up
- A permanent, verifiable statement that the accounts are one person. It cannot be retracted, and it applies retroactively.
- Suits
- Vendors with an established name and a deliberate reason, who have accepted the trade.
One key, kept quiet
- What you gain
- The feeling of continuity without publishing it.
- What you give up
- The link exists whether or not you advertise it. Anybody holding both public keys can compare them at any point.
- Suits
- Nobody. This is the option that sounds cautious and is not.
Why the link is different from a name
A shared handle is evidence. A shared key is proof, and it is proof anybody can check without your involvement, forever, including on platforms that no longer exist but whose data does. That difference is the whole reason this gets a separate page.
What a key is actually for here
Two things, and only one of them involves your own key. Checking the market signature, which uses their key and not yours. And signing or encrypting messages, which uses yours. The first is the important one and it does not require you to have a key at all.
What tips it
Whether you need to prove you are the same person as somebody else. Buyers almost never do, which makes a fresh key free. Vendors sometimes do, and then the question becomes whether the standing being carried is worth a permanent link that cannot be withdrawn later if either identity is ever exposed.