I'm not sure how it is a "good compromise" in any sense of that phrase. What is "safe" about this? What is "private" about it?
All it does is confirm that one person who signs up for reddit once signed up for an online email account somewhere. We are not stuck in 1998, where your one and only email account was created when you signed up for Comcast or Verizon DSL.
This makes the signup process for reddit slightly more convoluted, and maybe makes them spend an extra 6 minutes doing so. This is an insufficient amount of delay to expect them to have any life-changing epiphanies.
It does not prevent the harassment you are concerned about. It adds no safety.
It isn't private... as unimaginative as most people are, chances are that you can guess email addresses from usernames even if reddit does not reveal them. It actively reduces privacy, and much more so than you imply.
This is so far into the realm of security theater that if just stand there and wait 30 seconds, the costume department will come by and change you into your clown outfit.
I'm not sure it's possible to capitalize on this. It's simply not an outrage-inducing development. There might be hundreds that notice, and dozens that care, but of those most will be too lazy and unfamiliarity-averse to do anything about it.