Hmm, I did get a reply -- two, in fact. The first said:
Thank you for contacting eBay's Trust & Safety Department about an email you received from an address that includes '@ebay.com' but that may not be an authentic email from eBay. We will investigate this situation immediately.
Please be advised that there have been cases where people have attempted to gain access to an eBay member's personal information by sending "spoof" emails. Spoof emails intentionally give the false impression that they have been sent by eBay to solicit people to transmit their account information. Based on your inquiry to eBay's Trust and Safety Department, the email you received was likely a spoof.
[then a lot of stuff I'm not gonna paste here]
Later that day, I got a follow-up:
Thank you for contacting eBay's Trust and Safety Department about email solicitations that are falsely made to appear to have come from eBay. These emails, commonly referred to as "spoof" messages, are sent in an attempt to collect sensitive personal information from recipients who reply to the message or click on a link to a Web page requesting this information.
The email you reported did not originate from, nor is it endorsed by, eBay. We are very concerned about this problem and are working diligently to address the situation. We are currently investigating the source of this email to take further action. You may rest assured that your account standing has not changed and that your listings have not been affected.
[...and more stuff that I've deleted for brevity's sake]