[nix0n]

> On StackOverflow, anyone can edit any question. Anyone can edit any answer.

Neither of these things are true. In fact, to a user with zero reputation, StackOverflow is much more locked down than Wikipedia.

But the real issue with obsolete questions, is that a new question will be marked as a duplicate of an old obsolete question and closed before anyone has a chance to answer it.

So the real value of an obsolete tag would be that a new question couldn't be marked as a duplicate of an obsolete one.

[brudgers]

Low reputation users' edits get reviewed. A zero reputation user is no more likely to have flagging privileges than other privileges. Optimizing for the zero reputation user in regard to obsolescence doesn't seem like a productive approach to me anyway.