When you bid on BaT, you have to have your credit card number on file. So, you bid $10,000 on a car, they put a hold on that card for 5% of the bid (min $500.00USD), up to a max of $5K, until you are outbid. If you win, the CC is immediately charged. If you bail on a BaT auction as a no-pay, you lose the bidder fee on the car, which could be from $500 to $5,000; and you are forbidden from bidding, or even commenting, again. Are you gonna risk that kind of money just to "**** with the seller", knowing you will lose the money? Doubt it. Plus, BaT knows your IP info, so going in under a different nic won't work. Sellers often thank the bidders and commenters, that is normal on BaT. The commenters and bidders do a real good job at not being total assholes to each other, it is pretty much self-policing, and it works. I've been on BaT for over 11 years. It's a great venue, and is dirt-cheap to sell. Way, way better than flea-bay or CL. It is a superb deal for buyer and seller, which is why it is so successful.
Go to any classic car auction. Your buyer fee is normally ten percent of the purchase price, as is the sales fee. You buy a car for $75K at B-J. You also pay another $7,500 as the buyer. The seller pays $7,500 to B-J, as well. Now, on BaT, for that same $75K, the buyer pays a max of $5K to BaT. The seller would pay just $99.00 to list the car for 7 days, or $395.00 for a premium listing, and a 10-14 day listing. And BaT has an average of 40 auctions that start and end on any particular day. Note the number of high-end cars there? They're not stupid. Nothing "fishy" about it at all.