He agreed to a deal with a seller and once escrow was setup he backed out of the deal. This is a sign that he was trying to avoid using escrow and only agreed to accept escrow to avoid setting off any red flags to others. Despite this being a bad idea, often times people will simply agree to trade without escrow if one does not respond and setup escrow quickly enough.
A neutral rating is more appropriate then, since no coins were lost and no scam was attempted. People are allowed to back out of deals. You should put in the rating your belief it's a sign he was trying to avoid escrow.
The scam that was attempted was that he tried to scam the bitcointalk account from the seller. The reason given in this thread was something along the lines that he did not trust me, however that is contradictory to the fact that he asked me to escrow for him.
To perhaps come at this from another direction (tl;dr 14 pages over again), did worhiper_-_ ask you to escrow 1) before... or 2) after...
...reading a ToS from you to the effect of "Quickseller escrow terms are at the exclusive determination of Quickseller. Buyers and sellers do not get to set any escrow terms themselves."
If worhiper_-_ did knowingly violate that clear and effective ToS, then neg trust is warranted. If worhiper_-_ did not knowingly violate that clear and effective ToS, imagining that escrows are merely there to do whatever the buyer and seller agree the escrow should do, then neutral is.
If I were you, I would require escrow counterparties to clearsign their agreement to that ToS before PMing you anything else at all.
All of worhiper_-_'s terms and conditions of the trade were met. He wanted me to confirm the details of the account which is something that I did even though doing so fell outside of the escrow agreement.
Additionally, the purpose of escrow is to protect all parties involved. If there are terms that would put one party at significant risk (as was the case with the seller) then terms need to be adjusted to ensure that all parties are protected. If there was a condition when it would be impossible to tell if it was met or not if one party was lying then that condition is obviously not acceptable. For example if someone was buying BTC for cash in the mail, it would obviously make zero sense for a condition to be that no insurance be purchased if escrow is being used as it would be impossible to make any kind of determination as to who is lying if one party were to claim the envelope was empty/didn't contain all the cash that it should.