This is a real issue which deserves to be remedied. I think we (by which I actually mean: Stack Exchange developers, which I'm not) can fix this in a way that does not significantly decrease overall question quality, by:
- avoiding automatically converting anything into a separate question, but
- providing users with more powerful, easier, and better documented tools with which to reuse text from deleted posts.
I think the best solution to this problem is what I'd consider a "light" version of what Oli has suggested:
When a user's question or answer disappears for any reason, they should be notified.
I understand this violates one of Stack Exchange's current principles of notifications--that notifications should always be positive or neutral, and never negative. But the degree to which this violates that principle can be mitigated considerably by wording the notification politely, respectfully, and in a way that doesn't cause people to think a deleted post is something they should take personally.
Make sure all users can see all their deleted posts (both questions and answers) no matter what, and that those posts appear (though in a way that shows they're deleted) to them on their profile pages.
When a user views their own deleted post, provide an expandable section that explains briefly why it may have been deleted. This can be generic, but it should be more than a link to some other page (like the help). Of course it can link to the help for further reading.
For deleted answers, this short, easy-to-read expandable section should explicitly suggest that if the answer was really an attempt to get help with another problem (even if the problem is related), the user should consider posting it as an answer instead.
The user will be able to copy and paste it--or parts of it--into a new answer, because they will always be able to view the deleted post, and will always be able to find it by looking in their profile.
I believe the quality filters for questions and answers are currently different, such that some posts can be submitted successfully as answers but not as questions. This is based on a conversation I had with someone who couldn't post his question as a question, so he posted it as an answer (and we deleted it).
I'm not sure the system really does have this behavior, but assuming I am not mistaken (i.e., that it does), if we are going to make things easy on people and support the functioning of the system at the same time, then:
- The quality filters for questions and answers must have the same standards, or,
- the quality filters for questions must be at least as permissive as answers, or,
- whenever the quality filters for questions exclude something that would be permitted as an answer, there must be a more-specific-than-usual message to help the user fix the post.
We should solicit community input as to whether or not the message displayed when a quality filter rejects a post is clear enough that the vast majority of people will be able to fix their post. If it's not, the message should be changed.
I'm not saying the message should tell users precisely what it was about their post that triggered the filter. Instead, I advocate that even a user who has trouble writing well in English should be able to figure out how to fix their post with a minimum of effort (provided they have basic English reading skills, with which to understand the message).
This might already be the case but personal experience (see above) suggests to me that it might not currently be the case.
Finally, another improvement might be, for user with less than 50 reputation, to put a "Why can't I post a comment?" link everywhere "add comment" would appear for a 50+ rep user. One of the biggest reasons people post non-answer answers is that the site naturally encourages everything to be posted as a question or an answer, even if it should be posted somewhere else or not at all. Enough people make this mistake that the error is clearly in the site design itself more than it is in the users who post non-answer answers.
Such a link should expand to a small section of text, or raise a pop-up (similar to the popups raised by attempting an action like voting with insufficient reputation). New users should not have to navigate to a separate page to understand why they cannot comment. More generally, new users should virtually never have to navigate to a separate page to understand how to use the page they're currently on, except to optionally seek further reading on a site-related topic that they have already--and quickly--come to understand at a basic level.
