You're taking it too far. One should prefer delegation/composition in most cases, but if you're trying to direct users to a restricted reuse model (inheritance

You're taking it too far. One should prefer delegation/composition in most cases, but if you're trying to direct users to a restricted reuse model (inheritance), then it works fine and is often a much clearer approach than "Joe's custom delegation model". There are plenty of examples of this in practice - someone pointed out NeXT/Apple's UIKit for example elsewhere in this thread (which also uses composition where appropriate). The Java collections hierarchy is also a good one (LinkedHashSet < HashSet < AbstractSet).