Thanks for raising this. I think this should be addressed now.
This was my fault. You are right that, normally, downvoted questions can't be deleted if they have an upvoted answer. Here's what happened. Yesterday I dealt with a sockpuppet ring. This triggers automatic deletion of all questions with a vote score below 0 from the socks. I manually ...
I don't want to disrupt your suggestion, but I can make the following offer in the meantime:
If you see a good question that you think is of high difficulty and has a good answer that hasn't received the recognition or reputation points it merits, leave a comment here, and if I agree, I'll offer a bounty on it.