The OP is incorrect that we did this for just one site. We did it for several sites—all the sites we knew about which were punishing HN referrers and which users had complained to us about.
The consensus in the current thread, as well as in https://news.ycombinator.com/item?id=36249414 and emails, is that a better approach is simply to put noreferrer on outgoing links in general. I've made that change now.