Steve,

is only a forum in the buy/sell arena. They make their site available, and they collect fees for the use of it. They offer options and they offer guidelines, but their intent is to not be directly involved in any transaction....other than to collect their fee.

The guidelines that you quoted are open to any number of interpretations.

Your interpretation has a slight flaw, IMO:
"As I read it, you should leave feedback... when every aspect of the deal is complete. ...So if you're not satisfied because you didn't get feedback, it's allright by eBay to leave a neg."

If I win one of your auctions (1) I send you payment (2) You send me the item. We're both happy with the transaction, so far. ONE of us has to be the first to leave feedback, but the transaction isn't complete for either of us, because neither of us has left feedback...so neither of us can leave feedback, because it isn't complete?

"After you make a purchase or sale, remember to leave feedback for your trading partner."
My interpretation is that, once the seller has my payment, he's made the sale....time to leave feedback.

Yes, there's going to be a few times that a totally unreasonable person is going to leave a neg for someone who's left him/her positive feedback. All that can be done, in that case, is to use the "seller's response" or "buyer's response" feedback option.

One of my "favorite" examples of feedback gone awry was something like this:
Negative: This person was totally unreasonable, wouldn't contact me to resolve problem.
Response: HUH? I was the buyer and I'm happy with the item!

While I do think the seller should leave the first feedback, I refuse to fuss about it unless the seller actually states, in an email to me, that I have to leave the first feedback. When that happens I email them and explain that since I (as the buyer) sent payment promptly, I've completed my part of the contract and I expect them to leave me positive feedback. If they aren't willing to do that, they get no feedback from me.