This article states the buyer for a property in Annandale traded bids with the auctioneer who made vendor bids, pushing the price higher from $5.2 to $5.65 million. I was under the impression you were only allowed 1 vendor bid in NSW or has that changed now?
https://www.smh.com.au/property/news/buyer-who-fell-in-love-…
If the vendor bid more than me and me only I would stop bidding. If they won, they would then have to come back to me.