But nothing about the site is actually technically unique beyond the brand and its history. It means a LOT to OP sentimentally, but if this was doing some kind of amazing social good, someone could just go make a rails app for their CS degree's senior design class and we'd have a functional replacement back.

So, I think OP's decision to bury it makes a lot of sense. It's a very human decision and it doesn't really hurt anyone by him making it, and if you want to be super utilitarian about it, it's probably better to let them peacefully close this chapter and move on to whatever next interesting thing they're going to do rather than sour them on it and have them do their next thing more privately.