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. By hiring Quickseller as your escrow, you agree that you are bound by these terms."
If worhiper_-_ did knowingly violate that clear and effective ToS, then neg trust is warranted for depriving you of your escrow fee (time=money). 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.
IIRC, wohiper_-_'s version of the story is that he and seller negotiated some terms, sent them an escrow request to QS, who agreed, but then sent different terms back, once W saw QS's terms were different from the ones he agreed to with seller, he decided not to go, and cancelled. QS's argument is that anyone who doesn't accept my God-given perfect terms is obviously a scammer and therefore deserving of my wrath.
@TBZ and @Vod, also note that if you publically disagree with QS's actions, he can interpret your disagrement as an "attempt to weaken the trust system, and therefore scammy behavior" and will use that argument as a reason to neg rep you (he used this rationale to neg-rep me with his alt ACCTSeller, see my feedback page---effectively, if you disagree with QS, you are exhibiting scammy behavior).