For migrating to Stack Overflow, there are some good guidelines at What topics can I ask about here?. Quoting, specifically:
Stack Overflow is for professional and enthusiast programmers, people
who write code because they love it. We feel the best Stack Overflow
questions have a bit of source code in them, but if your question
- a specific programming problem, or
- a software algorithm, or
- software tools commonly used by programmers;
... and is
- a practical, answerable problem that is unique to software development
… then you’re in the right place to ask your question!
(emphasis on "bit" added)
What does this mean for Code Review members who are considering flagging/submitting for migration to Stack Overflow? Well, perhaps a few things:
Big "code dumps" with little or no explanation as to what the specific programming problem is are not good fit to migrate to Stack Overflow;
Software algorithms that don't have a clear explanation or definition of how they work (or how they are supposed to work and how they don't currently work as expected) are not good fit to migrate to Stack Overflow;
General questions about software tools, practices, design, etc. are not good fit to migrate to Stack Overflow;
Instead, perhaps consider Programmers.StackExchange, as long as it is on-topic for that site.
Questions that lack "a practical, answerable problem that is unique to software development" are also not good fit to migrate to Stack Overflow.
This includes questions that are very broad in scope and/or where answers would be largely opinion-based, and questions that are extremely narrow in scope where the answer(s) are unlikely to be useful to others besides the original poster.
As always, be courteous, be nice, and be careful before nominating a question for migration to Stack Overflow to make sure it won't be closed there for being off-topic.
One late but significant note
One additional note (redacted from a comment by Deduplicator):
As an aside, don't consider a lack of reaction [from Stack Overflow
regulars] as a sign that you were right [in migrating a post]; Stack
Overflow has such a high volume of posts that lots of them may slip
through the cracks. And in some cases, while the questions bad, they
just might not be bad enough to spend a vote on it, considering the
other targets which are also in the big pile of posts to triage/look
through in the Stack Overflow review queues.