Super User regularly gets "trolling" posts -- utter nonsense posted as an answer, like the same word repeated over and over to create a block of text, or random strings of characters, or someone simply commenting about how awful Super User is (unrelated to anything specific). There was one the other day where the "answer" was something like:
Question:_______________________ Answer: ________________________
These don't really fit the definition of "not an answer" or "very low quality" because they aren't really posts at all, they are simply trolling. It seems like a waste of reviewers' time to put these into the review queues.
Technically, they aren't spam because they aren't advertising anything. They might possibly be considered "abusive" under the offensive, abusive, or hate speech flag (in the sense of abusing the site and creating a waste of people's time).
These posts are more appropriate to flag than vote to close because moderator intervention may be needed to shut down the poster. What is the appropriate flag for this kind of nonsense?