There is only negative - neutral - positive on eBay (in the overall rating, not the specific shipping/as advertised etc. categories).
So it now comes down to expectations and how to match expectations to + 0 and -. I for one absolutely expect items to be as advertises and delivered within the timespan indicated. For that, sellers get a 0. If they deliver faster and/or a better item, they might get a +. If they fail to meet my basic expectations, they get a -. Hence, by these standards, the - was perfectly justified.
I did not know this is how the e-bay rating system works!
For some reason given this information, I changed my mind. When the buyer had 5 stars to choose from (in my mind, and I thought they granted only 1) it seemed abominable to leave the bad rating, given facts. Seemed to me like their customer service was worthy of at least 3 stars.
Now knowing that the scale is only three wide, it seems like a reasonable thing to do, leaving a rating of "minus".
So it now comes down to expectations and how to match expectations to + 0 and -. I for one absolutely expect items to be as advertises and delivered within the timespan indicated. For that, sellers get a 0. If they deliver faster and/or a better item, they might get a +. If they fail to meet my basic expectations, they get a -. Hence, by these standards, the - was perfectly justified.