That's really weird. Why would they send you an email asking you that? I was going to say, my account was compromised a few weeks ago and I had to deactivate that account but that was obviously a different situation.

If I were you I'd change your password to your email, set up dual authentication, and then deactivate your other Reddit accounts (if you still have any active accounts). Actually, before you deactivate your Reddit accounts, check your log in history - see if there's any unusual activity there. And, don't respond to them.

If you're really worried, set up dual authentication for all your online accounts and make sure you have a different password for each of them. So at least if they can access your Reddit account, they can't get to any others. Also, if you're really really worried, just to be cautious, you could make a post about this on Spinster and '@' the admin who has a tech background.