I called them on Monday, got cycled through three different people, and the third guy told me that their fraud prevention department decided that I was too high-risk to continue using PayPal.
I asked if I could talk to someone else; he said no. I asked if I could have more information on fraud prevention's decision; he said no. I asked "So there's nothing I can do?" and his response was "Yeah."
So... that's a thing that happened.
This is especially frustrating because I really don't see what I did that was that wrong. I waited a while before giving them documentation, and I probably shouldn't have... but once I decided to deal with the issue I gave them everything they asked for, rescanned documents that didn't go through the first time, and waited patiently for some kind of response. They never did tell me what was so fraudulent about my apparently unacceptable ID and SSN.