Once a puzzle is solved it might be moved to a forum of Solved Puzzles.
That decision would only have to be made once, by the OP or a moderator.
Solved puzzles would still be accessible and perhaps debated. Members simply
would be pre-informed that the solution is not still being sought. The current
forum might then be called Active Puzzles.
Chestnuts would remain a problem undiminished from the current state, but no
one [including moi] seems to know of preventive measures. Leave that as a
separate issue for now.
The spate of resurrection of old threads seems to have been contemporaneous
with the sudden popularity of the Brainden Gadget - bless it for bringing many visitors
who become members to the site. But I'm wondering whether the gadget feeds a
random sample of "whatever is there" [including the ancient stuff] to new users,
who then simply respond to the OP without inspecting the entire thread to see
whether it's been solved.
If so, the gadget could be made to operate only within the Active Puzzles forum,
and some of the rehash might be avoided.
- bn