If nothing else, we'd want some sort of attempt to establish that it really was released into the public domain (or under CC-SA).
A name isn't going to do very much to establish that. I could always make up a fake name and say that's the author. Or I could just lie and claim that I'm the author. Either way, you'd just have to take my word for it.
Some sort of attempt, not a foolproof attempt.
But I'd rather not lie.
Exactly. I'd be happy to accept the claims of the uploader unless and until there is reason to believe otherwise.
So I suppose anonymous works which aren't PD-OLD are prohibited?
A really good question, Anthony. I don't know. On the other hand, an anonymous work doesn't appear out of nowhere, either, does it. (Unless you yourself created it and want to submit it anonymously, in which case why not just make a throwaway account and use PD-SELF or something?)
Dan
I'm fine with trusting users who look like they deserve it. They are, after all, the ones affirming the copyright status of the image; unless I have a really good reason to doubt them I'm going to go with their call on these things.
Bots obviously lack such ability for judgment, unless they are human-augmented.
I'd even be fine with trusting an editor who hasn't been around a while, if the rest is plausible. But something like "anonymous" without further comment makes it look like "couldn't be bothered". Not knowing the bot, I'd have to guess it keys into exactly that word.
Dan