Having explicit guidelines is definitely good, Unfortunately, the sort of people who post straight to Main are unlikely to ever read the guidelines. This calls for a technical solution (e.g. all but meetup posts must be promoted to Main (manually or upon reaching some upvote threshold), not posted there directly, maybe with a few exceptions for admins and SIAI staff).
Having explicit guidelines is definitely good, Unfortunately, the sort of people who post straight to Main are unlikely to ever read the guidelines. This calls for a technical solution (e.g. all but meetup posts must be promoted to Main (manually or upon reaching some upvote threshold), not posted there directly, maybe with a few exceptions for admins and SIAI staff).