was going to quote more, but they have mysteriously disappeared...
They don't disappear "mysteriously". They are deleted, because they are off-topic here and distract from the real questions about Stack Overflow and the Stack Exchange network (which this site is about). See the FAQ:
Questions that are extremely off topic, or of very low quality, may be removed at the discretion of the community and moderators.
You as a user (not you, cbroughton, personally) are expected to post the question on the site it belongs to. There's no need for a migration path back to – for example Stack Overflow. I can't imagine you don't know Stack Overflow when you manage to post on Meta Stack Overflow. Even more so, if you repeatedly post off-topic questions on Meta Stack Overflow but already know how to use Stack Overflow, why should we do you a favor and migrate it back? In many cases, people post here to evade the low quality filter. That would be a way to circumvent it.
why would an open discussion question be down-voted?
Because people disagree with your idea of having them migrated. Voting on Meta, as you can read in the FAQ,
[…] works a bit differently from other Stack Exchange sites. On Meta Stack Overflow, voting is often used to express agreement or disagreement, not to point out a lack of quality or helpfulness
So, please take a minute to read the FAQs of the sites you are planning to post a question on. This will save you from surprising downvotes, closed questions and deletions.