[aruanan]

"the young can sometimes be wiser than we"? sounds awfully stilted unless you say: "the young can sometimes be wiser than we can".

That's just because you've grown up using defective English. ;-} The point of the sentence is that one is making a comparison between two groups: "They are wise. We are wise. Who is the wiser? They are more wise than we [are]". Both groups are described using the nominative case. The pronoun form of "us" is either the dative (meaning "to" or "for" or "on behalf of" us) or accusative case (the object receiving the action, "They hit us"), neither of which apply here. Do you say, "They spoke to Tom and I" or "They spoke to Tom and me"? Those who choose the former would be more likely to think that "wiser than we" is stilted or incorrect. They're wrong in either case.