No. A seller tapping bid on their own listing gets refused: You can't bid on your own item.
The bid is never placed. This is not a policy checked afterwards.
The same block in three places
Bidding on your own auction.
Buying your own item, from the cart.
Making an offer on your own listing.
All three are refused by the server before anything happens.
Why it matters that it is a refusal
A rule against shill bidding is only worth the enforcement behind it. A seller pushing their own price up against a real buyer is the thing that would make a live auction worthless — you would never know whether the person you were bidding against wanted the item or owned it.
Refusing the request removes the question. How do I know a show is not staged?
What the block does not cover
A second account, or a friend bidding on a seller's behalf. No code can see that directly.
Which is why the rules around it exist and are enforced hard: one verified number belongs to one account, bidding on your own items or asking others to is on the not-allowed list, and buying from your own store to inflate sales is too. These are suspension matters rather than warnings. What is shill bidding?
Saying this plainly is better than implying it is impossible. The block is real and it is not the whole defence.
What a seller legitimately can do
Set a reserve — a price below which it does not sell. That is the sanctioned way to protect a floor, it is set beforehand, and it is never shown to buyers so it cannot be gamed. What is a reserve price?
Not list something they are not ready to part with.
What they cannot do is refuse the result afterwards. Can I refuse to sell if the bidding ends too low?
If you suspect it is happening
Report it under Safety / report someone. Metzee can see patterns in the bidding data that you cannot — which accounts bid on which store, how often, and where they stop.
Signs worth reporting: the same handful of names winning everything from one store, or bids that arrive only while the price is low and stop at a plausible number.
The defence that always works
Your ceiling. If a price is being pushed artificially, you stop — and whoever pushed it past you has bought their own item. How to not get carried away
More: what is shill bidding, how do I know a show is not staged, how do I know the price is fair.