A while back DevForums migrated to a new platform. That did not lose any content. See this post for details. Moreover, in most cases old URLs continue to work, redirecting to the new location. There is, however, one case that’s still broken, namely URLs that point to the first post in a thread (as opposed to the thread itself) (r. 64589574). There’s no sign of that being fixed, alas )-:
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Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"