If our purpose is maximizing selling price, we need to know something about the buyer. For example I may own something like bogo.com , which I may be willing to sell for 10K, but 1M can also be possible. If I know the buyer is a real enduser, I may sell, if he is a flipper, I would know there is a real buyer who may pay 6 figures soon (before I die), and I would wait... (But giving full data of the buyer may not be good for the marketplace either because otherwise we may contact the buyer outside that marketplace and complete the sale elsewhere).
We own the domain, so we have ability and right to track buyer's IP. If we are parking at a marketplace, that marketplace should show us bidders' IPs. Marketplaces can also show domain part of bidders' email, or a little bit less, so we would know if it is gmail, or, yahoo, or godaddy, or a real company name.
Statistically most buyers at Sedo are lowballing flippers (and they may be using fake contact data, except email, so they can get invoice..), and there must be a way to stop this. Instead of showing buyer's data, they can require refundable 10 usd payment (refundable unless they cheat).
What I suggest is good for Sedo as well. If flipper sells for 10K, but I sell for 100, then I get 90 (minus 80 for other fees), and Sedo gets 10, and flipper gets 9900. But if I sell directly to the enduser via Sedo, then Sedo gets 1000 at least. Why not do this, would endusers be scared because their info is shown, not at all. Only flippers and investors (domainers) care about it.