You are right, the feedback section would probably be too tricky for private sales hence I was referring to registered sellers. For private sellers, unfortunately the I watch your back you watch mine is definitely the way to go in a public forum.

I've noticed that some ppl will post a How-Things-Went comment after everything is shipped and funds transferred. I did so when I purchased a set of OEM air ducts from another member (can't find the thread, but it's there somewhere). Look through the buyer/seller's past posts for those comments.

Same, and I like to leave my for sale threads open in case I did something wrong or vice versa, that it's out in the open.
And luckily a lot of us already "bump for a great seller" "bump for easy transaction" and things of that nature on a person's future for sale threads