I think the defining factor is what the "question" is, or the particular roles they play in meta.
Meta kind of covers the role the blog used to and is used for announcements
Something worth keeping in mind: when Jeff started the blog, meta didn't exist. The blog was meta: discussion, debate, even the first elections were all conducted there. Even after meta was created, it didn't work terribly well for announcements until we added network-wide featured posts in 2014
-from a comment by Shog9
If the question is an announcement - we're (ab)suing answers as a way to give feedback on the announcement - say for the shiny new post on openid getting deprecated, most of the answers are folks pointing out potential issues and pain points rather than a traditional answer, and that's pretty much how we roll.
These sort of announcements do not need to be official - The recent post on smoke detector adjusting thresholds mainly got feedback.
Ideally answers providing feedback should be substantially different (you can upvote in agreement, or comment to add on) from each other and actually provide feedback.
As a subset of those, we have massive lists of feature improvements and changes - which vaguely work like a traditional forum post. Answers here are literally meant to break up a insanely long list into system legal chunks, and they're more of an "infodump" than an answer.
I'd note, this is PROBABLY the hardest bit, since these arn't really answers but its one of the reasons we have meta at all - to have a place within the SE framework for people to interact.
We also have posts acting as community FAQs. There are a 'classical', and one might even say canonical case of community wikis - these should have a single answer covering the full range of topics.
It also acts as the user facing "issues"/Feature Request. Ideally answers here are closer to traditional answers - though naturally a official canonical answer is preferred. In many cases - its user supplied.
So, unlike a regular site, what a proper answer reflects the nature of the question.