A while ago, consensus was reached that open-ended puzzles are no longer welcome on our site. That means, if a question has no absolute "best possible" answer, so that any answer could conceivably be outdone in the future, then we're supposed to close it as too open-ended to work well here: there's no way to know when/whether an answer is optimal, and there could conceivably be arbitrarily many different answers.
We still have an optimization tag, though, and not every "find the least/most/largest/smallest" puzzle is off-topic. Quite often such puzzles have an answer which is provably correct. Hence why I posted an answer on that previous meta thread to clarify exactly what "open-ended" means. I also said:
If an absolute best answer exists and seems likely to be provable, then it's not open-ended: even if some answers are posted with successively better but non-optimal solutions, those are partial answers with increasing progress towards an upper/lower bound, not just iterations in an open-ended answer stream.
Nowhere on that meta thread was anything said about deleting answers. (You can check by searching "delet" on the whole page.) However, a few hours ago one of our moderators deleted all answers to this question except the one which brute-forced all possibilities with a computer - including the optimal answer which Bass skilfully found, as well as other answers which were optimal at the time of posting. The deletions were justified by the following comments:
Based on the rules established by this meta post and the consensus around it, an answer must have justification for why the solution is optimal. Without that, this is a comment, not an answer.
Apparently the "rules" he was thinking of was the following quote from that previous meta:
Optimization questions should have a provably best answer (ideally, not one that needs heavy programming or mathematics to prove, in the same way that we currently don't want puzzles that require heavy programming or mathematics to solve). Answers should come with justification of why they are optimal; an answer without this is not a full answer, but more of a comment.
But since the main discussion was about closing open-ended questions, it's arguable whether there's a clear consensus on deleting certain answers to non-open-ended questions as well. Neither the quote just above from Deusovi's answer, nor the other one from my answer, received any disagreement from the community ... however, they weren't really integral parts of the discussion, which was primarily about the handling of certain questions rather than certain answers to different questions. So here's a new meta to get consensus on this point.
If an optimisation-type puzzle is NOT open-ended, and answers are posted which give bounds on the solution WITHOUT proving optimality, should those answers be deleted?
- Q: Find the smallest possible number of X needed to satisfy Y.
- A1: Here's a way of getting Y with seven X.
- A2: Here's a trick that enables Y with six X.
- A3: Here's a proof that it can't be done with four X.
- A4: Here's a proof that six X is the least possible.
After (or even before?) A4 is posted, should any or all of the other answers be deleted? A4 is the only one that proves optimality, but the others all establish bounds, A2 is the actual optimal solution (only without proof), and A1 was the best solution found at the time of posting.