This is something of a formal expansion of this subrequest from Aarobot from a long old discussion on list questions, into a full feature request. I think we've long since gotten over the fear factor of list questions once we realized what the real problematic sorts of lists come off as.
Discussion, however, is still not an accepted medium on the Q&A site, with good reason. Our updated FAQs also state that questions asking for a discussion are not allowed. But we don't actually have a close reason that particularly adheres to it.
"Too Localized" and "Exact Duplicate" refer to entirely separate problems, so they don't apply as a result of being a discussion. The other close reasons all technically can be applied, but while we are functionally accurate in using them, they can serve very simple grounds for Meta arguments on semantics.
"Not A Real Question" specifies a very cookie-cutter list of attributes. Difficult to understand, vague, ambiguous, incomplete, overly broad, rhetorical, cannot be answered... all of which an be worded around with a discussion that is still not a question.
"Off-Topic" only specifies being off-topic with regards to the subject matter of the site. It doesn't cover the fact that our site, as a Q&A site, has certain kinds of threads that are in themselves off-topic.
"Subjective & Argumentative" specifies that the open-ended nature will lead to confrontation and argument. People tirelessly (and perhaps ironically) argue that the nature of their question is a peaceful discussion that is not argumentative, it's one of the most common oppositions to the S&A close reason overall.
I propose that either we get a specific close reason for discussion "questions" (the original request of Discussion or Poll
would be really nice, honestly), or we augment the Not A Real Question or Off-Topic close reasons so that they may semantically be applied to discussions. For example, add "is a discussion" to Not A Real Question, or specify that "We're a Q&A website, not a discussion forum for chit-chat" at the start of Off-Topic.