>What mechanism exists for determining editor error?
For positive errors, anyone may report problems -- and such reported problems get a VERY high priority -- most are reviewed within hours.
Since any editor with privileges and interest in a category can add sites there, and since no one editor can be required to add any site, omissions by any editor can't be considered error.
I know this is not what webmasters want. You want some way of controlling the editor, some way of imposing your will and your priorities and your desire on someone else.
But the ODP simply doesn't have that.
>Is that a royal or collective "we?"
It's a collective. The ODP has been facing this question for at least five years (to my personal knowledge), and I've personally been involved in at least four attempts to see what might be done without betraying the ODP ideals. And I can say that of my own experience, the community leaders have over that time grown less interested (even more hostile) to the whole idea.
There is a whole list of reasons why it's not a good idea -- as you could have read in the announcement. Different reasons weigh differently with different people. From the information-theoretic viewpoint, perhaps the significant philosophical issue is this:
(1) BEFORE a site rejection, WE DON'T HAVE ANYTHING TO TELL!
(2) AFTER a site rejection, WE DON'T WANT TO TELL THE SPAMMER ANYTHING!
There are no other possibilities. So, how do we deal with the very very rare case of accidentally-deleted suggestions (less than 1% of all suggestions)?
We don't. There are so many better things to do with our time -- so many more efficient ways to find previously-overlooked sites -- so many richer sources of URLs to mine -- that it just isn't worthwhile digging through once-rejected sites on the off chance that someone might have been a mistake.
You see, the ODP is designed around editor efficiency. If the editors are efficient enough, sites will be found by multiple methods, and no single method is critical. It's better to let the editors focus on the rich sources of URLs, rather than trying to suck out the last dregs of ONE minor supplemental source (that is, site suggestions.)
It's all very simple, as soon as you stop thinking about site suggestions as a tool for working your will on other people, and start thinking about it as a very minor way of helping people who are perfectly willing and able to do a good job without your help. And, at the same time, stop thinking about editors as "powerful", and start thinking of us as we really are -- that is, merely helpers and participants in a community that could go on just fine without any one of us. If I had never participated in the ODP, it would still have achieved something like it has achieved (not perhaps exactly the same), after a delay of two weeks. What kind of power did that give me?