Sometimes answers are posted, which almost comply with the specs. They might be a clever, interesting take on the problem, but not follow one of the rules, or the program might crash in a few rare cases. What should be done with these answers? Upvote, downvote, or delete?
Depending on the question/answer, I'd say leave a comment pointing out the flaw and wait for the user to fix their answer. It wouldn't be fair for others to allow the answer to stay, but on the other hand deleting is too harsh for an answer that almost works.
If fixing the answer breaks their clever code, then they can leave it in their post as a bonus footnote if they wish.