When are closed questions deleted?

Question

In the last few days I've noticed several closed questions getting deleted. This would be unremarkable if I had been noticing a steady drizzle of these all along, but I haven't. Maybe this has something to do with how I noticed the recent deletions, which is by some unusual rep changes. That would only happen if I answered a question that was ultimately closed, and had non-zero rep from that answer.

However, this brings up the question of when/if closed questions are deleted. Many closed questions are total crap, and I'd expect them to be deleted quickly. Others may be poorly asked, but yet gather some decent answers. Does the system just delete all closed questions eventually, does a mod have to clean them out, or something else?

For example, see DC Motor reversing relays using a micro switch. It was poorly asked and I can see why it was closed, yet Andy and I both wrote useful answers that I don't remember being covered here otherwise. If a automated process eventually deletes closed questions, then that's just the way it is, but if a human looks at each one, then what's the criterion for deletion?

Related to this, there seems to be a bug in how the rep change from such a question is accounted for. I got one up vote and one down vote on the deleted answer, for a total of +8. I'd expect to loose that 8 when the question is deleted. Yet the rep for the day shows both a -8 and a -2 for that answer, which I don't undertand. On the other hand, the rep total for the day looks like it's calculated for a net -8 due to the deleted question. Please understand I'm not quibbling about the miniscule rep difference, but either there is a bug to be pointed out or I've got a misconception about how the system works that I'd like to clear up.

Answer 1

StackEchange has an automatic cleanup script, which deletes closed threads, if they fit certain criteria. Details, more details, related.

The example question** in the O.P. has a score of -1, and both answers have the score of 0. It fell under the last category "abandoned closed", I would think.

** It's visible with 10k+ reputation.

*** I'm inclined to undelete the question, while leaving it closed, because the answers are useful. But I'll wait with that to preserve the context of this meta thread for the purposes of discussion for a little longer.

Answer 2

As a general mention, if you put a decent amount of effort in an answer, then it is in your interest that the question is not closed. If you understand the question enough to offer a useful answer, try to edit the question to improve it, upvote it, or mention (in the question comments) why the question is OK. Closure is the first step towards (potential) deletion of a question.

The close system is intended to prevent this situation from happening in the sense that ideally the question would have been closed before anyone posts an answer. The first close vote came right as Olin posted his answer, and Andy posted about 30 minutes later. The first close vote puts it in the Close Vote Review Queue, where it gained four more close votes.